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  1. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    Replaced the other 3 #8 transistors on the positive rail tonight. Adjusted bias per the service manual, Distortion levels are good for 1/4 watt up to 250 into 8 ohms from 20 to 20Khz. Heat sink much much cooler with the bias properly adjusted on the hot channel. Adjusted for 0.1 % THD with no...
  2. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    I have a couple distortion anaylers I use for setting the bias and troubleshooting. I'll probably hook it up tonight. The distortion at mid and high power levels is fine. My bigger concern is low level output.
  3. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    The collectors on the output transistors on the positive rail are at 60 VDC and I think the emitters on the negative rail are at the lower rail voltage as well (-60). I'll reconfirm tonight. I can confirm that the rails switch to plus and minus 90 VDC tonight as well under high output...
  4. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    I really like the molex connectors in your photo. was that unit also wire wrapped originally? While troubleshooting the heating issue, I somehow took out one of the positive rail output transistors. The SCR crowbar went into action and shut down the output. That is good to know. I wish the...
  5. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    Well the 30 VDC on the output is now gone but the channel is running hot on idle. Have to check the bias across the emitter resistors I guess. It was a bear getting the wire wrap back on the posts but it worked out pretty good. There was enough slack that I was able to get them all wire wrapped...
  6. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    Thanks for the link. Very interesting,.
  7. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    Thanks for the feedback. Something to consider. I'll do some more research before I decide what to do for the input capacitor. My ears are probably far from "golden" at age 60. I avoid getting my hearing tested cause I don't want to know how bad it is these days. Anyone else have opinions...
  8. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    I was planning on using a Muse bi-polar. I have quite a few in my capacitor stash. I need to check the values to see if I have a 22 uf. I try to keep a good supply caps on hand. I ordered a bunch last month to recap a pair of Sansui Ca 2000 preamps and a TU 919 tuner. I just finished a Marantz...
  9. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    Great Thread. I was following it when I picked this unit up 2 weeks ago. I was in Bangalore India on a business trip when I saw this one on EBay. I used the buy it now option. The funny part is the seller lives about 15 minutes from my office. I ended up paying for shipping even though the...
  10. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    So do you think the best bet is to rewire and replace the wire wrap with molex type connectors? Some of the wires are on removeable connectors on the wire wrap posts. This might be an easier route and the wire lengths would be OK. The concern would be getting good surface contact.
  11. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    A big thank you for putting me in the right direction. R11 22K on base of Q4 was open. Hopefully there won't be any other issues. I need to order some caps and possibly some replacement transistors so that I can match for the input stage The other channel has a 150 mV DC on the output...
  12. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    On Q4 base, R11 22K is open. No physical damage to the resistor. I will continue to check every component on the board. This looks to be the problem. :banana: Makes me wonder if I should change out all of the resistors. I'll replace the electrolytics and the input transistors with a matched...
  13. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    The 120 ohm resistor is good. I had been trying to avoid taking the board out of the amp to trouble shoot but decided to do so today. This should cut down the troubleshooting time significantly. Glad I have an electric wire wrap tool. Its going to come in handy when I am done. If the...
  14. mpavkov

    Happy Birthday to dr*audio

    Happy Birthday Warren From another former KSU Audio Clinic participant By the way, I purchased a Soundcraftsmen MA 5002 based on your past recommendations. Trying to fix a bad channel with 30 VDC on the output. Any help would be appreciated.
  15. mpavkov

    Vintage 80s/70s amp war

    The KA 3500 was my first amplifier, purchased it new for something like $250 in the early 70's. I liked it a lot better than the Pioneer SX-525 which was my first receiver. The only issue I ever had with it was the limited power rating. When we would crank it up loud at parties in college, it...
  16. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    I was hoping you would chime in. I see you have been very active in past threads on the Soundcraftsmen amps. I'll take a look to see if I can find the 22 ohm resistor. This amp is in beautiful cosmetic condition. I will need to convert the inputs over from large guitar amp style phone...
  17. mpavkov

    Soundcraftsmen MA5002 Bad Channel - Help

    I picked up a MA5002 in very good physical shape knowing that it had a bad channel. Since wire wrapped boards make this a bit of a pain to work on, I thought I would seek out some advise on troubleshooting. Here is what I have MA 5002 B series s/n 30 VDC on the output of the bad channel...
  18. mpavkov

    Possible to use Model 18 transformer for Model 20?

    I got the price for the rewind in case anyone else needs one rewound. Price is $190 but will be worth it to get the tuner back up and running. I went back to the unit and I see that I pulled one of the DC filer caps already. I'll go back and look for any shorted caps or other issues that could...
  19. mpavkov

    Picked up a lot of Marantz Gear Today

    1060 Photos Here are some of pics of the 1060 for anyone interested.
  20. mpavkov

    Picked up a lot of Marantz Gear Today

    The 1060 amplifier surprised me as it really sounds great. I hooked it up to a pair of New Large Advents and was very impressed with its sound. I had to use some fader lube to clean up the switches and the mid range pot. The power switch was sticky but freed up after a little lube. All the pots...
  21. mpavkov

    Possible to use Model 18 transformer for Model 20?

    I haven't yet but that was my first guess. Since they are in in open view and are metal cans, I'll have to restuff them if they are shorted or try the company that offers new cans for old equipment like the McIntosh's. Thanks for the suggestion.
  22. mpavkov

    Possible to use Model 18 transformer for Model 20?

    Transformer rewind ? Great, I follow up with him.
  23. mpavkov

    Possible to use Model 18 transformer for Model 20?

    Model 20 Transformer Thanks for the feed back on the 18 and 19, Size wise it makes since since they are receivers. Well the transformer was very hot and insulation vapor (smoke) pouring out of it. Perhaps it's not shorted but the transformer was definitely "smokin". I was so disgusted...
  24. mpavkov

    Picked up a lot of Marantz Gear Today

    Initial Pictures Here are 8 of the 12 units Need to find some space in my bench racks for these puppies.
  25. mpavkov

    Picked up a lot of Marantz Gear Today

    I dropped off 4 of the units at my office on the way home (the receivers and tape deck) . Too much to carry into the house at one time. I'll bring them home on Monday. I had about an hour and a half ride each way from where I picked them up. I left the three receivers and the tape unit at my...
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