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Old 12th March 2006, 04:44 PM   #11
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Yes sir, the pic you posted has the same manufacture stamp as the trans in question. This zapco is a 4 layer board which makes it more fun to deal with. I did a quick check on the SMD's (caps, res, transistors) around the leaky caps and did not find any shorts but I know that the caps leaked and I have to clean it up. I just hope that it didn't ruin the layers beneath. I can't believe that zapco made such a bo bo with caps in such an expensive product. I show that it listed for $1499 back in 1998. The date stamp on the board is 1994. If I get really stuck on this, I might send it to justrepairs.com or somebody that can repair this particular model and pay the money. I really appreciate the info on the transistors. I'll keep chugging away and scratching my head.
Thanks
Scott
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Old 12th March 2006, 06:53 PM   #12
Eva is offline Eva  Spain
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Any equipment with four layer boards is a pain to repair. For small signal and digital circuits it may be OK, but in power applications traces and plated thru-holes in the inner layers tend blow without you having any chance to notice.

Also, with the usual single or double sided PCBs you have a chance to draw your own schematic and trace any fault, but with four layer boards you just can't do that, so a schematic from the manufacturer is required.

Concerning Zapco, don't get fooled, extreme complexity, high prices and a lot of hype doesn't necessarily mean reliability at all. You may actually find some low-cost Chinese amplifiers to be more reliable than those ultra-complex high-priced models.
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Old 12th March 2006, 09:53 PM   #13
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Your right, they were not very helpful and they will not give up a schematic. I've had luck with soundstream emailing schematics to me for the old reference and rubicon amplifiers. I have them for the ref 1000s and the rub 1002 if someone needs one I can email the pdf file to them. Some of the old orion amps (sx series) switching power supply semiconductors made buy GE are getting tough to find. The zapco looks like it was never abused. All the traces are clean and not bubbled. Just by looking at it with the naked eye, you would never see that the caps leaked. I give it my best shot to fix it.
Scott
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Old 14th March 2006, 04:27 AM   #14
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Perry,
Do you know who made these jfets? My guess is SSI but I don't know...
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Old 14th March 2006, 04:32 AM   #15
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Old 14th March 2006, 11:39 AM   #16
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Siliconix/Vishay.

This site has logos for many of the electronic component manufacturers. It may be helpful in the future.

http://info.electronicwerkstatt.de/b...teile/ic_logo/
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Old 14th March 2006, 11:11 PM   #17
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Awsome, thanks. And thanks for all the responses.
Scott
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Old 15th March 2006, 12:30 AM   #18
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Default siliconix part number j109

The jfets in this zapco have the siliconix part number j109 next to their symbol. This amp has eight of them but 4 have a number C448AB and the other 4 have C436AJ. The data sheet for j109 covers all eight as being the same. What would these other numbers indicate? Are they some kind of S/N or manufacture sequence. Basically, would it be safe to replace all eight of these with the j109? Just wondering...
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Old 13th May 2006, 07:20 PM   #19
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Yes the J109ís are just JFETís and thatís that. I did finally fix this amp and posting to share and maybe help someone else. The caps did leak and replacing them is all that I did. THEY DID NOT DAMAGE the board. I found a timing issue with a HCF4093 QUAD 2 INPUT NAND SCHMITT TRIGGER located at U20. The 10uf 50v cap connected to pins 12 and 13 was making the amp not start all the time. I found this when I removed the cap and the amp started every time. I opted to put a 100uf 50v cap in its place and everything works fine. So after replacing all the out-put finals, power supply MOSFETís, full wave bridge, all 12 op-amps and many caps, it turned out to be just the four leaking caps in the preamp stage and the timing issue. It sucked working on a four layer board without a schematic!, THANKS ZAPCO FOR ALL YOUR HELP! (NOT). Just thought I would share.
Thanks every-one for all the help and advice.
Scott
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Old 13th May 2006, 07:38 PM   #20
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NAND gate before
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