Re-capping a Pioneer CT-F1000 Cassette Deck

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pustelniakr

Silver Miner at Large
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It is time to take on a "major" re-capping project: a super sweet Pioneer CT-F1000 KCU (US/Canada model) cassette deck (a 3-headed beauty), built in March of 1978. I have already restored the transport to full speed, replacing "all" rubber drive parts (belts, idler tires, pinch rollers), lubricated and aligned mechanically, and DeOxited all sensor micro-switches. The motors (of which there are 2) required no restoration, which is typical for this model , unlike her sisters: CT-F900, CT-F950, CT-F1250, which usually all need the reel motors to be rebuilt.

This thread is intended to chronicle the massive re-capping project that this unit presents.

Here is where I am at the moment. Now for the bottom line so far: There are 16 circuit boards in a CT-F1000, and 166 electrolytic caps to replace. Let's just say that I'm quite intimidated by the task, since these bad boys are not designed to be disassembled to the degree that I will have to (daughter boards are soldered to the mother board, inter-board connctions are made via wire-wrap and soldered, individual wires).

I will chronicle this thread with abundant photos as I go. If you intend to follow in the path I blaze, you will need a cache of fresh pace-maker batteries.

Enjoy,
Rich P
 
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pustelniakr

Silver Miner at Large
Staff member
Vintage Restoration Boiler Plate

First a bit of boiler-plate DIY info:

1. If you are an impatient individual, tending to get frustrated, and force things, or get rough. DO NOT attempt this operation. You could very easily wind up with a pretty, brushed aluminum paperweight. Generally, if a unit is fresh, and unmolested, it is less expensive for a knowledgeable tech to restore/repair. If I have to clean up a ham-handed, fumbled job, it will definitely cost ya.

2. Make sure that your tools are in good condition. For example, if the tips of your screwdrivers are worn, you will damage the heads of your screws (some are in pretty tight), and you will play heck trying to get them out. New screwdrivers make all the difference in the world. All it takes is for your driver to slip one good time in a stubborn Phillips head screw, and you could make it next to impossible to remove, and you will damage your driver as well (take a look at your old Phillips screwdriver).

3. Do not get curious about additional details of the mechanism. There are an abundance of tiny little parts just waiting to jump out of your machine and into the nether world if you are not careful or know what to expect. These little parts can be worth the entire cost of your machine, since, if you do not find them, or if you break them, you will have a non-functional unit.

4. Unless you have an eidetic memory (photographic), take pics, notes, etc., as you go. It is not a good thing to have extra parts left over at the end of a job. I have a large supply of tiny zip-lock bags which I use to put parts from various stages of work. In this way the number of screws, or a couple of screws and a spring or c-clip will key my memory to the stage or assembly they go back into.

5. There are no magic bullet chemicals. Use each chemical or lubricant, etc., only where it is appropriate. If not, you have a paperweight again. If you are not sure what to use where, seek wise counsel, from reputable sources.

6. Before you do any disassembly or work, put a baggie over your power plug, and hold it on with a rubber band. The very last thing you want to do, is get surprised by a spark, or G_d-forbid, a jolt. Guess what...paperweight time again.

7. NEVER force ANYTHING. If you have to force it, you are not doing it right and you will likely break something, or get a part on wrong...paperweight time again (Getting irritated at that phrase? Good.).

8. Mickey Mouse has no part in a vintage restoration shop. NO half-tail operations, no funky monkey rigging, no time bombs for someone else to clean up. I cannot tell you how many times I have seen serious just enough to get by kind of repairs (blobs of glue to replace lost c-clips, weird wire twists holding on broken parts, etc.) If you break or lose something, buy a parts unit and replace it right. Chewing gum, bailing-wire rigs will ALWAYS come back to bite you.

9. There are innumerable tricks of the trade that are too detailed to discuss in a DIY thread (how to hold a tool, how to keep a c-clip from jumping across a room, etc.). Be prepared to learn some/many of them the hard way (by experience). Sorry folks, it comes with the territory.

10. Get a service manual. They are just too readily available to justify flying blind. If you are a cheap ________, buy one on CD. They are only around $10 on the bay. I prefer originals. The color coding in the drawings is a real help to an old man like me.

11. Go slow. Be meticulous. Double and triple check everything. It is easier to take the extra time to do it right the first time, than to have to take the time to troubleshoot and repair any mistakes.

12. When wires are attached to boards being worked on, try to tie them to the board, so that the wires will flex at the tie-point, rather than at their attachment points. This will keep you from making stressed connections that will break in shipment or later. Also, note wire bundle ties and remove them, to gain as free access as possible. You may be moving the boards around quite a bit, accessing top and bottom, over and over again. Please take special note, even photos, of which wires are in which bundles, and where they are tied in bundles. If you just bundle up wires to look nice, you could get wrong wires in close association with each other, and introduce hum or other kinds of noise or feedback loops.

Last but not least...I accept no responsibility for how well or successful you may be at performing this operation. Results will vary from unit to unit, and from individual to individual. You know...some folks should simply not try this kind of work. Most folks can be successful however.

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Re-Capping: Motivations, Considerations, Results

My experience: Recapping generally yields only an incremental improvement in the way a unit sounds, but should significantly increase the life-expectancy of a unit.

Here are your incentives/motivations, so balance them against cost and/or effort:

1. I have measured a large number of caps, replaced during a recap. The majority are at or below the low end of their specs, unless they are in a location where they get thermally stressed.

2. When 'lytic caps go, as the odds of doing so rises rapidly once their rated life expectancy of around 20 years has been reached or exceeded, they go any one of 3 ways, drift out of tolerance, fail open, or fail short. They all drift, and statistically, failing open or short is about a 50/50 mix.

3. If a cap fails open, you may notice, you may not, depending on where it is in the circuit. Generally the fault is easily repaired, with minimal peripheral damage.

4. The main risk: If a cap fails short, it can, and generally does, take out significant associated circuitry (ie., semiconductors made out of unobtainium).

5. Recapping is cheap, part-wise, averaging $0.35 per cap, but labor is high. A good tech can be counted to be able to replace around 10 caps per hour (including unit disassembly, cap removal, pad cleanup, cap installation, and flux cleanup). Even if the tech only charges $10 per hour, in a unit with 150 caps to replace (not uncommon on gear I work on), the labor really mounts up when it takes 15 hours to do the job. Typical modern labor costs are in excess of $60 per hour. Haven restoration artists are not in it for the money (but money is nice), so we generally do not charge anywhere near that rate, but our labor is worth that rate.

6. The MOST IMPORTANT aspect of a recap, is the opportunity to refresh all circuit board solder joints. Flow-soldered connections have only about a 30-year life expectancy. In my experience, I have solved more problems caused by old, oxidized, fractured solder joints than by failed/drifted caps. Here is where the real bang for the buck is realized, and MUST NOT be underestimated.

With all of these aspects considered, recapping is really only a viable procedure for upper end gear, unless the gear owner is an avid collector, and wants all of a series in excellent condition, etc.

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping Boiler Plate

Now a bit of boiler-plate recapping info:

Note: Most of the original capacitor series used in these old units are long obsolete. Selecting replacements, from current manufacturers and their series, is also a task requiring a qualified tech. There are many parameters to consider (operating temp, value, value tolerance, life expectancy, effective series resistance, internal losses, size, etc.).

I am a Pioneer specialist, so, all my work references the Pioneer parts series. This is because my master recapping database is based on Pioneer part numbers.

The problem with most vintage gear (in excess of 25 years old), is the fact that electrolytic caps tend to dry out, since the electrolyte is moist, and must stay that way for proper function. Some caps drift severely, in the lower capacitance direction. Some caps fail open, and simply cease to perform whatever function they were designed in to do. Others that fail, do so by failing short, generally causing catastrophic damage to the unit. You may be enjoying a ticking time-bomb. Some will swell and leak, causing all kinds of corrosion damage to the circuit boards in the area, while others will literally blow up. Some caps measure OK on a capacitance bridge, but, in the circuit, leak DC, causing noise, bias shifting, instability, etc. I truly recommend re-capping gear you intend to keep and enjoy, or sell to someone you care about.

Re-capping generally requires a complete service manual, with all published supplements, addendums, errata, and modification sheets. Each board is gone through, electrolytic caps are each measured to get their physical dimensions (replacements must fit in the space provided). Not to fear, normally, since modern caps tend to be 1/3 the size of the originals (sometimes causing other problems). Then the caps are checked to see which Pioneer series they are in (indicated by Pioneer part number). Now you must attempt to determine what characteristics were important to the designers that established a specific Pioneer part number series. Hints come from what cap manufacturer series was used (usually, and hopefully, more than one), "if" you can find the very old data sheets you need (so far all the series I've encountered have been long obsolete), or mfg-to-mfg cross-reference lists. You must also track what kind of circuits the particular Pioneer part number series is used in (coupling, de-coupling, filtering, feedback, etc.). Without the original Pioneer part drawings, you must engage in significant guesswork, supplemented by informed/experienced reverse-engineering.

The next step is to attempt to find modern manufacturers for parts that conform to the design criteria determined in the previous step, followed by locating distributors that handle the replacement parts (in the onesy-twosy quantities you will need), and determine the per unit cost. (Note: I prefer to keep things original. I don't try to second think the original designers, unless the future owner pays significantly for an upgrade or modification. I do tend to use a bit better part than the original, but not to point of using the very expensive, esoteric, sometimes snake-oil parts). It gets to be a lot of fun when the part you need is not made by anybody in the size and/or voltage you need (like finding low voltage electrolytics in the sub-1uf values). Then you need to substitute a different kind of part altogether.

I then created an overall Pioneer database for electrolytic caps, which I can then draw on for other models down the line, and from which, I create a model-specific database, which shows each cap, on a per-circuit-board basis, with all the associated info (original part number, dimensions, value, working voltage, new mfg part number, distributor part number, price, etc. etc. etc.). The database also contains a table of consolidated data, where all like parts are grouped, used as a purchasing list for the model.

Here are some of my choices for the various types of caps that may need replacement:

1. For the low leakage or low noise lytics, I use Xicon LLRL series parts.

2. As to the standard 85degC, 20% lytics, I prefer to use the Panasonic FM series. When they are not available (possible, since this is a new series for Panasonic), I use the Panasonic FC or the Nichicon PWs. They are an incremental upgrade to the originals, in that they are 105degC, lower ESR parts, low tan-theta (relating to internal losses), plus, the Panasonics are pretty, with those gold labels and all.

3. For standard 85degC, non-polars, I use Panasonic SUs. No upgrade here, but there are fewer choices in this type.

4. For the parts "requiring" low ESR, of course I'm using the Panasonic FM, and FC Nichicon PWs. No upgrades in this case, except for the temperature tolerance.

When I order the caps for a unit, I usually order enough to do 3 or 4 units, since I usually have at least that many units of any particular model in my inventory, and I like to have the parts I need on hand when it comes time to do them. That way, I also have complete recap kits on hand for incoming restoration commissions. I also usually order at least 2 extra of any particular cap value. In that way, my on-hand inventory of caps grows, at minimal cost, which helps to cover the cases where the manual states the need for one value, when a particular board/unit actually has a different value (happens when designs are changed during the production of a particular model).

Emphasis:

Recapping is not the panacea for modern man. Recapping is the last thing I do to a unit, other than cosmetic work and final/performance testing. I won't recap a unit, until I have determined that it is fully functional. Recapping is more for an attempt at adding longevity to the mix. The last thing you want is for a 30-year-old 'lytic to fail short (they also fail open, and drift out of spec). Recapping is not a good "repair" technique (falls in the realm of 'shotgun repair' which I hate).


Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Supplemental Recapping Operations

I have done alot of recapping, and I like to test the old ones every now and then, to see what their condition was. In general, I have found that they are not far off, just at or below the capacitance spec for the parts. I have found a few bad ones. What I add, with a recap, is a retouching of every solder joint on the affected circuit boards. Here is where the real problem is, in my experience: old, oxidized, fractured, and cold, joints that have failed. The life expectancy for a wave soldered joint (used in circuit board manufacturing) is right at 30 years. They tend to oxidize, and fracture, etc. I have repaired more problems caused by bad PCB solder joints, than by bad 'lytic caps, by at least an order of magnitude. So, for me, the solder joint retouch is the more important aspect of my recapping service.

When replacing a cap, I have found it to be best to remove the cap, then remove the solder from where the cap was. That way damage to the circuit board traces and pads are minimized. If you try to remove the solder, then get the board to let go of the cap, you will find that there is too much heat, time, and stress on the circuit boards, resulting in lifted solder pads and traces. The best method I have found is as follows:

1. Heat one lead/pad and rock the cap out a bit on the heated side. Let the pad cool and repeat with the other lead...working from side to side until the cap comes free.

2. Before removing the cap from where it came out, look at the cap and circuit board, to verify that the polarity mark on the silkscreen matches the polarity of the cap. If there is no polarity mark on the board, put one with a Sharpie. If the mark on the board does not match the mark on the cap, you will have to do a bit of reverse-engineering, with the schematic and board layout, to determine which is correct. Don't assume that the way it was installed was right, mistakes are made in factories all the time. The polarity marks on circuit boards vary. With Pioneer, there is generally a plus sign where the cap's positive terminal goes. Other manufacturers may use a dot, but that will generally indicate the negative terminal of the cap. The caps themselves generally mark the negative lead on the label, and make the positive lead just a bit longer than the negative one.

3. Once the old cap has been removed, go back and remove the old solder from the board, where the cap came from. Depending on accessibility, you can use a solder sucker (plunger-type suction tool), or solder wick/braid (braided copper on a roll, impregnated with a bit of rosin flux). I usually use the wick for hard to reach places only.

4. Form the leads of the new cap to fit the holes (so there will be some strain relief, and there will be no stress on the new joints. Then install the new cap, and solder, leaving a nice clean, well-formed, slightly concave fillet ("the bigger the blob, the better the job" is definitely a bogus concept). Trim the leads, so that there is just the slightest amount of lead left extending out of the solder joint. Do not cut into the solder joint.

5. When all the caps (and other parts) have been replaced, use a soft toothbrush and alcohol (Techspray 1610-P or Chemtronics Flux-Off NR 2000) and clean off all the new and old flux from the board. This will take a while, since the old stuff tends to be abundant, and doesn't dissolve as easily as it would have if cleaned off when fresh. When doing this, Make sure that you do not drip off of the board into coils and pots (etc.) of other boards or into mechanism. The flux in solution will not be kind when the alcohol carrier dries. I usually put a couple of layers of paper towel to catch the drippings.

While you have a board loose, it would behoove you to de-solder and remove any heat-sunk drivers, clean off the old heatsink grease, and apply new heatsink grease (I use Dow Corning 340). Be very careful to reassemble exactly as they were assembled. many drivers are electrically isolated from the heatsinks, using mylar isolators or some other method. If you don't put them back together the way they were, you will let the magic smoke out when you apply power later. Putting fresh heatsink grease on will help to keep your old parts cool so they will last longer. Old, dry, flaky heatsink compound does not do its job.

Note: Styrol (polystyrene) capacitors are extremely sensitive to heat. They cannot tolerate temperatures above 85 degC, and will be damaged is subjected to higher temps. Soldering involves temperatures in excess of 200 degC. You must clip a heatsink clip between the capacitor and the solder joint when retouching joints associated with styrol caps. To be safe, unless a magnified visual inspection of a solder joint, related to a styrol cap, reveals the need for re-flowing (oxidized, fractured, etc.), I generally mark the solder joints in close proximity, on the same trace, with a red sharpie. This is so I will not hit them with a soldering iron during the solder joint retouch operation performed on the board, once all the 'lytics have been replaced on it. The sharpie ink is usually removed when I clean off all the old and new flux from the board, after solder retouch. The attached image shows a couple of styrol caps, so you can recognize them...

02 - Styrol Caps.jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
An Initial Visual Overview

As I said before, there are 16 PCBs, with 166 'lytics to replace. There are no super large valued caps to try to ignore, so ALL are going to go. The total per deck cost turned out to be only $35 in parts. The labor will be another thing all together. Except for the low-leakage Xicons, all the parts came from Digikey. So far Digikey has been perfect (not one component extra or shy, all parts filled correctly), and I have made some truly complicated orders (like this one).

As I stated previously, I picked up enough to do all 4 CT-F1000s in my stable, with a couple of extras in each value, for good measure. I find that it works better to do gear in batches, when possible. Each unit gets easier and faster and the quality of the work improves with each unit that way. Two CT-F1250s are next.

The attached pics are nice "before" pics. If all goes well, you will not be able to tell the difference from the "after" shots, unless you look real close...

Nudie Front.jpg

Nudie Insides.jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Power Supply Board

OK...I decided to do one of the harder PCBs to access, first. There is nothing like facing your fears, head-on. I haven't got the guts to do the control board, yet, but I may do that one next. As it turned out, the power supply board is easy to look at, but hard to get to, to change out parts. I had to remove the back panel, then move the transformer, fuse board mount, and accessory A/C outlet.

Then I covered the control board (under the transport) with a few stiff layers of cardboard, and moved the transformer up on that, then folded the back panel (power cord still attached) over the front top of the unit to get it out of the way and to have better access to all sides of the power supply board.

The power supply board had 13 caps to change, and most of them were big enough to see the effects of modern technology. As long as the can is bigger than the minimum can size, the difference in size is quite dramatic. Several of the new ones were less than 1/3 the size of the originals, physically.

While I was at it, I decided to freshen up the solder joints, since flow-solder has a more limited life span than manually applied joints, especially since I saw a couple of questionable joints. (I have to remember to get me one of those old soldering heat sink clips before I do any of the audio related PCBs, since they have several styrol (polystyrene) caps, which despise heat, and could easily rebel at their ripe old age)

Chicken that I am, I put the back panel back on, measured the power supply outputs, and played some tape for a while, to ensure all was well...It was. :D

Here is a pic of the unit without her backside:

PwrSpplyAccess.jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Control Board

I just finished the control board. I really thought it would be harder to get at that it was. Actually, Pioneer and a bit of spacial relationships sensitivity made it a piece of cake.

As it turns out, 2 small caps were not the same value as the schematic and parts list. I always buy a couple of extras of each value, so I had an extra of the variant value of one cap. Then, the other cap actually used the original value of the first variant cap, as its variant value, so, I only have to buy more of the 1st cap's variant.

There were a total of 19 caps on the control board.

Before I move on to the audio-related boards, I decided to do a more thorough functional test, and found that the 400Hz test tone (used for user-calibration of the Dolby record level on a per tape basis) is not being produced. Everything else works fine. Needless to say, the test tone generator board is next.

The pics show the controller board in its fully assembled state (now you know why I was initially intimidated by it), the controller board made accessible, the controller board before recap, and the controller board after the recap. If you compare the last two, you can begin to see the difference in old and new cap sizes...

ControlBoard.jpg

Control Board Access.jpg

Control Board Before.jpg

Control Board After.jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Test Tone Board

Well...the test tone generator board was next. Here is where the recap served as a direct correction of a failure. The board was not generating the 400Hz Dolby Cal tone. As it turns out, one of the 3 'lytic caps on this board, a 2.2uF, 50V, output coupling cap was kaput.

Apparently, another, so called, tech had been into this one because there were probe pokes all over it. If I had just proceeded to recap the board, without the functional test, I would have never known that it had a problem with the cal tone (which someone else had given up on). The 2 2SC711-E transistors both checked to be OK with a meter (its a simple 2 transistor oscillator circuit).

I replaced the 'lytics, then retouched all the solder joints (a couple looked OK but questionable). Then, I used the legendary jumper cables and powered up the board outside of its mother board installation. 400Hz was there, right on the money.

I didn't really take pics during this process, because, I was in troubleshooting mode, but I have taken a pic after re-installation (so you can at least see what it looks like, after recap and repair). Note that there are several nice mylar caps on this board.

The pots and switches are real scratchy, and look to be hard to get to for recapping the volume assembly. So, in keeping with my tendency to do the hard stuff 1st, the volume assembly is next for recapping.

Test Tone Board.jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Volume Assembly

Well...I finally found the "Pain in the Neck" factor.

The volume assembly required the removal of the entire face section of the chassis, in order to get at the bottom of the board for recapping. That was just the beginning. Once I recapped the volume assembly, I decided to DeOxit all the user controls (front panel pots and switches) because I do it on all the gear I do, plus, several of them were manifesting problems.

The real pain began when the output fixing section of the test tone switch (fixes the output level, bypassing the output level pot) was not cleaned up completely by a simple spray and actuate operation. I had to take it out for some up close and personal work (disassembly and manual contact cleanup). That required accessing the bottom of the main board (mother board), lifting it up and sliding it forward a couple of inches. Easier said than done (by a long shot). The back panel had to removed again, and de-soldering that switch was something I don't want to repeat for a very long time. I didn't lift any pads in the operation, and that's a good thing (actually no pads lifted at all so far with this unit).

In and out, up and down, panels shifting all around, a real pile of metal spaghetti. When it was all reassembled (no extra hardware left over), I found that I had broken a wire off the pause switch board ('cause it wouldn't pause). I was actually surprised that was all that got broken. Now a full functional test again, to make sure everything works and the intermittent controls were successfully cleaned up, they were. Now the smile slowly creeps back onto my face, sheepishly, at first. The hard parts are now complete. I can relax and enjoy the rest of the recapping.

Whew! I think I'll do another PL-630 before I do the next CT-F1000.

The attached pics show the disassembly level necessary to recap the volume assembly, as well as an after pic of the volume assembly (fully installed). The frustration factor was so high during the main-board bottom access and switch repair operation, I'm sorry to say, I didn't think of you guys, so no pics of that level of disassembly (I also didn't want to scare you off, and I would have, believe me). I hope you will understand.

Volume Assy Access.jpg

Volume Assy After.jpg

The next step will be recapping the 4 Dolby boards (left REC, right REC, left PB, right PB)...

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Dolby Boards

After a bit of distraction, doing some commission work for fellow audiophiles, and some necessary work to checkout my new CT-F1250 (transport rebuild, and removal of swollen pinch rollers to have Terry Witt make some new ones), I'm now officially back on the job.

Folks, the hard parts are over. Access should be easy from here on.

The Dolby boards can easily be de-soldered from the main board, and worked on separately, on the bench. What a relief. Access is provided to the underside of the main board, via an access panel on the bottom of the unit (1st pic).

There are 4 identical Dolby boards: left and right record, and left and right playback. To minimize the impact of the operation on pre-alignment performance, number each board and put them back in the same positions as they came out of. Also, do not mess with the position of the pots at this time.

Due to the inability to find .33uF, 10v, low-leakage, 'lytics (audio coupling caps), I chose to replace those (lower left corner in the pics) with a .33uF 50v polyester film. Significantly bigger, physically, but causes no problem in this case.

As usual, don't forget to re-touch all solder joints on the Dolby boards. 30 years is too long for wave/flow soldered connections.

The pics show the bottom of the main board, visible through the access panel on the bottom, the Dolby boards installed in the main board, and the Dolby boards before and after recap.

Bottom Access.jpg

Dolby Boards Installed.jpg

Dolby Boards (Before).jpg

Dolby Boards (After).jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Playback Flat Amp

This one was pretty straight forward. The board came out for work, like the Dolby Boards. The only caveat was an internal conflict in the service manual. The part list showed a 0.47uF, 50v cap, while the actual cap and the board assy drawing showed a 35v cap. Since the caps I'm using for std cap replacement do not provide a 0.47uF cap in 35v, I went with the part list, 50v value (single voltage step up, so no risk with modern caps).

As usual, a retouch of every solder joint.

The pics show the Playback Flat Amp, installed next to the Dolby boards, as well as "before" and "after" pics. Note: some significant reduction in physical size...

PB Flat Amp Installed.jpg

PB Flat Amp (Before).jpg

PB Flat Amp (After).jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Playback Equalizer Assy

The Playback Equalizer Assy, is the 1st amp the the PB heads see. You can bet there will be some low noise, high stability parts on it. You would win that bet.

This board recapped in a straightforward manner, similar to the Dolby boards, except that the head leads remain connected throughout the process. You need to find a way to position the board and route the leads, so that flipping the board, front to back (done frequently), is done by a 180 twist of the leads. This is to minimize stress on the connection points.

The first non-standard caps to consider are the orange ones near the top, center of the board. They are a 4.7uF, 25v, low-leakage 'lytic. Fortunately, I found a direct replacement, in a Xicon LLRL series, from Mouser. It is even nearly the same color (for what that is worth).

Don't move the pots at this time to minimize impact on the pre-alignment performance.

As usual, re-touch all the solder joints, with one MAJOR exception, having to do with the other special caps on the board. Notice the unusual looking caps at top center. These are styrol (polystyrene) caps (one of the closest to the ideal cap that there is). Stay completely off of the printed nodes to which these caps are directly connected, or you will likely damage them. Their drawback is their sensitivity to heat. They just cannot take more than 85 degC. Soldering temps are normally far in excess of that. You need to connect a soldering heatsink clip between the solder pad and the body of the cap if you must solder them. Styrols of this type and form are very rare and expensive today. If you open up your gear, any kind, and find an abundance of these, you have a truly high quality piece of equipment. They were quite expensive even back in the day.

The pics are of the PB Equalizer "before" and "after"

PB Equalizer (Before).jpg

PB Equalizer (After).jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Meter Amp Assy

The Meter Amp Assy recapped in a similar manner to the PB Equalizer, de-soldering it from the main board, but keeping the leads connected at the top. Orient leads and board so as to minimize stress on the lead connections to the board, as you flip the board back and forth, during the process.

Remember to re-touch all solder joints, and to leave the pots untouched.

The pics are "before" and "after". (Note: You can really see the size differential between the originals and the modern replacements on this board :yes: )

Meter Amp (Before).jpg

Meter Amp (After).jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Integrated Circuit Amp

I decided to do the left and right integrated circuit amps next. These boards provide the mike, record, headphone and flat amp stages. Before somebody asks, the amp IC is a PA4001 (quad-amp).

I got my 2nd demerit, on this project, on the 1st of the 2 IC amp boards. I broke a wire connected to the top of the amp, and had to solder it back on. To make sure I didn't do that again, I took the wires connected to the other board and secured them to the board via tywrap and a hole that seemed to be put there just for the purpose. In that way, no stress was placed on the wire connections and the wires had to bend in the middle.

These boards had another sub-1uF, low voltage, low leakage lytic (0.68 uF 10v). As before, I sub'd it with a 0.68uF, 50v polyester (Panasonic V series). The holes were laid out in the board perfect for it. You can see it in the middle of the bottom of the board. Also, this one had another low leakage part, for which I was able to find an actual modern replacement (10uF, 16v, replaced with a Xicon LLRL series part, from Mouser) -- visible near to where the wires connect to the board at the top (orange).

As usual, all solder joints were touched up.

The pics show the IC Amp assys installed, and out for recap (before and after).

IC Amp (Installed).jpg

IC_Amp (Before).jpg

IC_Amp (After).jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Record Equalizer Assy

I just noticed...we're coming up the back stretch. Anyway, The Record Equalizer Assy was nothing special (only 2 caps on it). However, I did find a fractured solder joint near the top, on one of the coil leads :)

As usual, all solder joints were touched up.

The pics show the board installed, as well as a "before" and "after" pic.

Rec Equalizer (Installed).jpg

REC Equalizer (Before).jpg

REC Equalizer (After).jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Peak Amp Assembly

The Peak Amp Assy is next. It only had 2 caps on it, but it had the complication of having 3 wires to leave connected. No broken wires this time.

This board provides the Peak detection function and drives the "Peak" indicator, when the input signal gets to +5db, or more, while recording.

All solder joints were retouched as usual.

The pics show the board, buried under that cable bundle in the center of the pic, as well as "before" and "after" pics.

Peak Amp (Installed).jpg

Peak Amp (Before).jpg

Peak Amp (After).jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recapping the Main/Motherboard Assembly

Here we are, at the last board. 18 caps spread around in tough to get at places.

During this project I got pretty good at rocking the caps out a little at a time, then cleaning the solder off the pads, after the caps were gone (primarily using a solder sucker). I could not get to most of the caps on this board with my fingers. So, I used solder wick, and removed the solder with the caps installed, and freed the caps, picking them out with a pair of hemostats (installed the new ones the same way).

This board has 6 of those nice styrol (polystyrene) caps. Heat, above 85degC, is deadly for these. So, when it came time to re-touch all the solder joints on this board, I took a red sharpie and colored every joint that was in direct contact with one of the styrol caps (meaning: don't solder here). The red color came off when I cleaned the flux off. This was one scummy board, so it took alot of isopropyl alcohol to clean it up.

The pics show the main board "before," "after" (hard to "see" the difference), and the bottom of the board "after."

Main Board (Before).jpg

Main Board (After).jpg

Main Board (Bottom-After).jpg

Enjoy,
Rich P
 

pustelniakr

Silver Miner at Large
Staff member
Recap of the Recap

Stats:

* 16 Circuit boards to recap
* 166 caps, total, to swap out
* Total parts mismatch between manual and actual part: 2
* Total mis-ordered parts (incorrect value, or missing from original order): 1
* Broke 2 wires, and had to solder them back on
* "Partially" lifted 3 pads (Only the corners of C-type pads, so no problem)
* Total part cost: approx $40
* Total labor: approx 26 hours

Results:

* Test tone inop, corrected: bad 'lytic coupling cap, found/cleared by re-cap
* Intermittent record equalization problem (attenuated highs), corrected: fractured solder joint on REC EQ board, found/cleared by solder joint retouch
* Various areas of need for electrical alignment almost cleared. Only a minimal need to align/calibrate this unit now.
* This unit records on std bias tape so that you can almost not tell which is tape and which is source (Dolby on or off). My wife could not tell. Only the disappearance of hiss indicated that Dolby is in. Remember, with 3 heads, I can monitor the tape as I make it. I could not tell the difference between the various settings: Dolby in/out, etc.

This will be a real nice machine for somebody (probably me :) ). I will be replacing all 3 transport sensor micro-switches (just because), performing a complete alignment/calibration (REC/PB/Dolby), and polish her up real nice.

These last pics show the baggie of old parts I took out of this unit (maybe I should sell these "vintage' caps on the bay :smoke: ). And, oh, I thought you might like to see what she looks like with her clothes on. Just know that I have not polished her up yet (that's last).

Old Caps.jpg

Complete.jpg

I've 3 more of these to to recap (2 with rack mount ears), before my vacation is over. But, first...I think I'll re- foam my new AR9s...

Enjoy,
Rich P
 
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