Harmon Kardon PM 655 Help - No voltage left channel and no sound

[Zrooney]

A small update before I button this baby back up and test it out


After adjustments to the D.C balance and idling current I am getting (from the speaker posts)

Left channel:-.017VDC
Right channel: -.046VDC

Super Sneaky Edit: It appears as though the right channel is not working properly. It crackles and pops, and is extremely ,muffled. However the amp does work in Mono mode. It is getting late so I will update this thread tomorrow with what I find as well as looking at the things mbz said to.

 

[jheu02]

I forget whether you have another unit you can use as a preamp and one you can use as a power amp. If you do, pull the jumpers and see if it functions correctly just as a preamp (send the preamp out signal to a separate power amp's inputs) and vice versa. It will help you figure out where to look for the muffled sound.

 

[mbz]

After adjustments to the D.C balance and idling current I am getting (from the speaker posts)

Left channel:-.017VDC
Right channel: -.046VDC

Service manual calls for less than 10mV dc offset, most AKers strive for this. You may need better trimmers (VR's) like the multiturn type.
However this can wait, better to sort out the crackles/pops/muffle on the right channel. Since amp ok in mono mode, can rule out speaker
selector.

As jheu02 has suggested, need to try and localize the fault as either preamp or power amp stage. This is really a new issue, cause
could be anything from bad contact (wire, solder joint), failing components (transistor....)

 

[Zrooney]

I think I found the problem. I was running my input through the Aux/ Video in, which runs through the Phono board. This board has some of the lavender caps that jheu02 was talking about, and sure enough one of them was leaking fluid on the bottom(you can lead a horse to water, but you can't force it to drink haha).... I plugged my input into the tape inputs, as these go directly into the main pre-amp/amp board and the unit worked great. So given this I will be re-capping the phono board, and while I am at it the front panel board and getting back to you guys.

Before I put an order to mouser in, what are the VR multiturn trimmers that you are talking about mbz? If they are cheap I might as well throw them in the order, shipping is not going to change much.

 

[jheu02]

VR1,2 (DC Offset, 50Kohm)
http://www.mouser.com/ProductDetail/Bourns/3296Y-1-503LF/?qs=sGAEpiMZZMvygUB3GLcD7sSg8po3Zpo3Jw9dNzVbut8=


VR3,4 (Bias, 200ohm)
http://www.mouser.com/ProductDetail/Bourns/3362U-1-201TLF/?qs=sGAEpiMZZMvygUB3GLcD7u0h%2b6dv3D2BuC/ywhIS6sY=

You can see the trimmers in the very first post, very first pic of my linked restoration thread on the first page of this thread.

Make sure you seek and destroy all the lavender and blue Matsushita caps, ordering new. For the lavender, I'd use Nichicon UKL based on where I've found the lavender ones in various circuits. I'd have to look at the scat about the blue ones as to what's a good sub. As for the green TK caps, or the red ELNA audio caps in the phono section, I didn't find any of them bad. I still replaced all the TKs with modern caps I had on hand. I left the red Elnas as I wasn't planning on using the phono section.

 

[jheu02]

You'll need to determine a couple things before placing your order such as:

1. Do you plan to keep the unit long term? If not, fully restored will fetch more money than most parts left original.
2. Will it be a daily driver in your system? If so, full restore will insure fewer problems...it's 30+ years old now.
3. Will you be listening to albums and if so, what type of cartridge MM, or MC? Also, see question 1.
4. Is it worth $30-50 in parts and your time?

If you can tell, I lean toward full restoration in most cases since it's a hobby to me and "bench time" is free. If I keep the unit, I know it'll be good for years to come. If I sell it, that same work is a good selling point.

A full restoration is different from a "recap" and will include the following:

- Fixing any known problems
- Full switch cleaning and lubing as appropriate, sometimes to the point of disassembly of the switches
- Electrolytic capacitor replacement, small values being replaced with film caps
- Desolder, clean, regrease, resolder all heatsink-mounted transistors.
- Replace known troublesome/noisy transistors with modern known-good substitutes
- Replacing fusible resistors with high quality Metal Film
- Checking/replacing any power-type resistors (usually over 1W and up to about 5W, most cement types check out OK)
- Inspection and reflowing of solder joints, especially those that take abuse (rca connections, high heat areas...)
- Selective replacement of resistors in the audio signal with low noise metal film (mainly if I intend to keep the unit)
- Setting bias and dc offset According to the SM. if there's no adjustment for dc offset, I may replace the differential pair of transistors with matched modern types when available to lower the offset closer to 0mV if it's higher than I like to see.
- Replacing any burned out bulbs

I may have missed some things, but you get the idea. As you can see, it's a bit of work, but if I'm opening it up and pulling boards, I'd rather do the work once than replace things piecemeal as they fail or become troublesome. These steps also may just save a proprietary chip or other component that would otherwise render the unit to boat anchor/doorstop status if failed.

Thoughts on this unit next post...

 

[jheu02]

Open up your SM and follow along with what I'd replace if I were doing it. This SM is actually quite nice as the schematic has signal flow arrows through the various circuits. As a general statement, if there is a capacitor directly in the path of this arrow, not perpendicular or off to the side, it's a coupling capacitor, and your choice of cap to use as a replacement could have a direct effect on final sound quality. MTF over on the Pioneer forum (mainly) has done experiments regarding noise level in circuits where these coupling caps are replaced either with a high quality low ESR cap such as Nichicon UPW vs high quality low leakage cap Nichicon UKL and has found the noise level to be noticably higher if you do not use low-leakage caps in these positions. His caveat is that the ELNA Silmic II series MAY be an exception to this general rule. He did not look at "audio series" caps in his tests, so I won't comment on others.

Starting at the phono amp you have MC input, follow the arrow through the Left channel. You arrive at C703, 704 10uF/50V (Right channel has C704,706). These are probably red Elna for Audio in your amp. I left these in the one I restored, however, if you want to replace ALL electrolytics, you can use either Nichicon UKL or an audio cap such as the Elna Silmic II, Nichicon KZ, FG, KW... depends on budget.

MM signal traces through C601, 602 10uF/25V (also probably red Elnas). Same types apply here: UKL, Silmic II, other audio. Following the signal, you'll see it eventually flows through C621, 623 (L ch.) C622, 624 (R Ch.). These are placed back to back effectively making a single 10uF/25V BIPOLAR cap for each channel. You COULD replace these four caps with two Nichicon UES Muse bipolar caps (legs would go in the (-) pads straddling the (+) pads. OR you could purchase 10 x 10uF/50V caps for all of the above phono positions (C601,602,621-624, 703-706). Yes, it's OK to increase the voltage rating of your caps over stock as long as it's reasonable...1-2 steps over is fine, so going from a 25V cap to a 50V cap is fine. More on this later as it regards bulk purchase discount pricing.

I'd almost wager that 50V is overkill even in the MC amp, as the local filtering caps are only 16V, so I'm guessing H/K engineers felt the higher voltage rating would lead to lower noise, especially important in a MC circuit. However, I go with the rating actually found, listed on the scat, or higher than either in that order.

The filtering caps at C707-710 (330uF/16V) and C725-728 (330uf/25V) can all be replaced with 330uF/25V or 35V. I like the following series for my GP filtering and Power Supplies Nichicon UPW, UPM, UHE or Panasonic FM, FR, FC. I've also used United Chemicon KZE series and there's a couple others. I purchase at least 10 or 25 of each of the values so I get the discount pricing and buy the ones that cost the least as I consider them all roughly equivalent. I will also check the ripple specs depending on location used and decide on the series with the best ripple rating (even at higher cost) if I feel it's critical (usually in the Power Supply circuits). These series also are all rated to 105C, so that means they'll generally last longer than 85C rated caps.

All of the above is only important if you use phono or intend to sell at some point. If you want to save time/expense and don't use phono, ignore it all. I don't recall any of these caps being lavender or blue sleeved, but if they are, you want to replace those regardless of whether you intend to use he phono sections or not. More next post...

 

[jheu02]

Next Up: Other inputs through to the outputs.

Follow the arrow out of the phono board to where it enters the function switch. Then through the Tape Monitor, subsonic, high cut, stereo/mono mode, balance and volume (path shows all switches in off or cutout).

Bass Contour
Though you may never use this feature, I bet you have some blue or lavender sleeved caps in the following places: C901,902 (0.1uF/50V), C909,910 (0.22uF/50V). I'd use the following as replacements:

http://www.mouser.com/ProductDetail...=sGAEpiMZZMv1cc3ydrPrF7l45uRd9dVhNMAgEbMEkvU=

http://www.mouser.com/ProductDetail...=sGAEpiMZZMv1cc3ydrPrF7l45uRd9dVhhpJU3UAC2QY=

There's also a pair of local filtering caps at C905,906 (100uF/25V). Use the earlier mentioned series as replacements for GP.

Tone Control
C507,508 (10uF/16V) and C519,520 (47uF/16V). Probably lavender. Replace with:

http://www.mouser.com/ProductDetail...GAEpiMZZMtZ1n0r9vR22U0HJIc3SC%2bokRjGJOnCWvg=

http://www.mouser.com/ProductDetail...GAEpiMZZMtZ1n0r9vR22U0HJIc3SC%2boUCMynatiayM=

Pre Driver
The signal path enters this board through C401,401 (100uF/10V). When I redid one of these I used 100uF/25V Silmic II. These caps are physically larger than the original which resulted in me having to move two resistors to the trace side of the board so that the caps would lay flat to the board. You could also use UKL or other audio cap here as with the phono board. You could go to a 16V cap, but I wouldn't use lower than that anywhere. The lower voltage caps 6.3V and 10V seem to have higher failure rates than higher voltage caps (annecdotal evidence based on various or testing done by several...notably ConradH). If it were mine I'd use these based on MTF's research:

http://www.mouser.com/ProductDetail...=sGAEpiMZZMtZ1n0r9vR22Xou3HnuIKwrKRXpzjNQsMQ=

That's it for signal path caps on this board.

C405,406 (47uF/25V) I'd use The GP caps I listed earlier.

I'll wrap things up with my next post on the Power Supply, Protection, and Power Driver boards.

 

[jheu02]

Power Driver
C413-416 (330uF/50V) I'd purchase 10 of the following and also use them in the PS at C17,18,21,22. Great ripple current specs and price break at 10. Worth the extra money over UPW or UHE IMHO.

http://www.mouser.com/ProductDetail/Panasonic/EEU-FM1H331LB/?qs=sGAEpiMZZMtZ1n0r9vR22ZGaUoI0JcRfmPNxo6wMh3Q=

C411,412,417,418 (10uF/16V) I'd use 10uF/25V. Any of the earlier listed GP/low ESR caps are good here. However, you could also use the UKL recommended for signal coupling if you wanted to get a bulk discount. They are also rated for 105C, and though the low leakage spec isn't required for the circuit, it certainly won't hurt it. ESR of the UKL should be at least as good as OEM caps, though I don't know whether a very low ESR rating would be more beneficial here than the low leakage.

Power Supply
Main filters C6-9 (4700uF/50V) they are probably fine. I replaced them on the one I rebuilt, but the caps I used are no longer manufactured (Panasonic TS-HA series). If you elect to replace them, these would probably be a good alternative:

http://www.mouser.com/ProductDetail/United-Chemi-Con/EKMH630VSN472MA30S/?qs=sGAEpiMZZMtZ1n0r9vR22dBjIkbB%2b54Ph8yi77xDSLc=

I've used this series KMH in other builds and they're a nice cap. With main filters it's important to check cap length, diameter, lead spacing, and type of terminal (snap-in, lug, screw) in addition to looking at other parameter of ripple, ESR etc. i don't remember the size of the original caps, so the linked ones may not fit correctly. Check size before ordering. Some rebuilders will increase the capacitance of the main filter caps. This is OK to do, but needs to be in reason because the inrush current when initially powering on the unit can stress the rectifiers and or power switch if you increase it too much and the rest of the supply wasn't designed for it. For this amp, you could probably increase to 5600 or 6800uF caps without having to modify rectifiers, etc.

C17,18,21,22 (330uF/25V) see notes under Power Driver

C23,24,52 (100uF/16V) I'd use these:

http://www.mouser.com/ProductDetail/Panasonic/EEU-FR1E101/?qs=sGAEpiMZZMtZ1n0r9vR22eOLaseCUKTaoN7VUs8mR5E=

C51 (100uF/50V) I'd splurge and get this since it's a single cap:

http://www.mouser.com/ProductDetail/Panasonic/EEU-FR1J121/?qs=sGAEpiMZZMtZ1n0r9vR22WPtSjuqjALifC5PBG359sY=

Ripple, voltage rating, ESR, rated life span, and the 120uF because many modern caps tend to be on the -20% capacitance value rather than on the high side. You could use 120uF for C23,24,52 as well, or choose a 100uF cap here. I could have done that with most of the other caps but didn't want to go overboard as to explanations etc. Coupling caps you want as close to the circuit value as possible many times as different values can change the frequency response, timing, etc. depends what the cap is doing in the circuit.

Protection Circuit
C10 (4.7uF/50V)

http://www.mouser.com/ProductDetail/WIMA/MKS2C044701M00KSSD/?qs=sGAEpiMZZMv1cc3ydrPrF7l45uRd9dVhlTzVLqs2mUg=

C11 (33uF/10V)

http://www.mouser.com/ProductDetail/Nichicon/UPW1E330MDD/?qs=sGAEpiMZZMtZ1n0r9vR22RH2kZvTh%2b0aI97%2b5F7yVFI=

That should do it for capacitors.

As for fusible resistors, it's your call whether to replace them or not. Older ones tend to drift high in value. I would at least check them with one leg lifted from the circuit and see if they've drifted. If you decide to replace them, go with the same resistance value AND wattage rating in a quality 1% Metal Film resistor from the likes of Vishay, KOA Speer, Yageo. DO NOT INCREASE THE WATTAGE RATING. These are used as protection devices that are designed to fail if put in say an overcurrent situation, hopefully protecting more important components.

For instance R657,658 on the phono board are 22ohm 2% 1/4W fuse resistors. This would be a good sub:

http://www.mouser.com/ProductDetail/KOA-Speer/MF1-4CC22R1F/?qs=sGAEpiMZZMu61qfTUdNhG0RUkTLGOdTM5Aw3tcgTPKU=

It's got a high voltage rating, 1%, and the 50ppm rating means it maintains it rated value more closely as temperatures rise.

If you want another type that in addition is also very low noise, Vishay Dale Mil Spec are the way to go:

http://www.mouser.com/ProductDetail/Vishay-Dale/RN60D22R1FB14/?qs=sGAEpiMZZMu61qfTUdNhGwBiNiGBqN/zCoYgYTVM/yM=

Though you may actually want to go with the RN55 series due to the Mil Spec rating system to force the lower wattage rating. The commercial industrial equivalent CMF60 is rated at 1/2W for the very same resistor, whereas the CMF55 is 1/4W. These Dale resistors are excellent!

Here's the CMF Industrial datasheet to compare against the RN datasheet

CMF: http://www.mouser.com/ds/2/427/cmfind-239942.pdf
RN: http://www.mouser.com/ds/2/427/cmfmil-223788.pdf

 

[harman/kardon]

Harmon Kardon?

 

[jheu02]

Since the spelling of Harman Kardon is so important to you, why don't you ask the mods to correct the spelling every time it's wrong. Non subscribers can't do it on their own. At least that would be somewhat helpful.

 

[mbz]

Comprehensive guidance to a new member will undoubtably give a fine result. Years of experiance in a nutshell.

 

[jheu02]

On vacation and was having a lazy morning/afternoon, so thought I'd dig into the scat a bit to help. I normally am more general about specific caps and don't provide specific links because things go out of stock, etc., and there's more than one way to do things. But digikey and mousers's website search parameters can be a little difficult to navigate sometimes, so I thought with someone new to actually provide some links along with the general guidance.

 

[Zrooney]

Thank you jheu02, I was not expecting this at all. I was sidetracked last week and trying to get some money together to order the caps, and this is more than I could have asked for! Thank you so much! I hope you had a good 4th.

I just want to say, you guys are awesome! So much better than the cassette forum i visited before, where I asked for help and it turned into a giant pissing match regarding Nakamichi gear.

 

[jheu02]

Well, there's never any guarantees, but I hope it helps.