Help with inspection of ADCOM 565 I might buy

[wadejg]

I'm going to go inspect/maybe buy a pair of Adcom 565's. They are supposed to have had the input caps replaced and had some upgrades done such as replacement of input rca's and speaker binding posts with Cardas parts. The guy has a receipt for the repairs/upgrades. The work was done by:
Music Technology - Repair and Upgrade Services

So, how do I tell if the input caps are really in good shape. I figure I will take a multimeter and check the DC offset. Anything else I should look for if I take the covers off. I'm astute, but not knowledgeable about electronics.

Thanks for the help,
Justin Wade

[wadejg]

So the receipt for the amps has the following:


GFA 565 x 2
One mono stopped- yellow markings

parts:

6x 220 microfarad 35V FC
1x LTIOR IC
3x 1/2 W FP res
2x MPSA13 kistors????(resistors???)
2x MPSA63 kistors????
1x 5A3AG
2 pair Cardas BP
1 pari Cardas RCA
2x 5.0 microfarad 200V Auricsp????
1foot silverwire
2 LM329 zeners
shop supplies

parts $296.34
labor $475

Notes: Rebuilt both amps- did extensive cleanup from caps that leaked elctrolyte (very corrosive) onto adjacent ciircuitry. Upgraded connectors and input coupling caps. Set bias and checked both amps.

So, do people think that the input caps on both amps were fixed, or just one? I would really rather figure out and have the input caps on the other amp replaced before it causes any problems and leaks too. The shop is an Adcom certified repair facility so I would hope they know that the caps are bound to fail in both amps at some point.

Help appreciated,
Justin Wade

[anatech]

Hi Justin,
I can see that some repairs are due to the electrolyte leaking out and the damage this can cause. The big question is if they did a complete job or not. That electrolyte can be really hard to get rid of sometimes. I have an Adcom amp in right now that is being really stubborn, the worst so far. The PCBs are stripped down right now. The rebuild will be like building the amp from a kit.

There are many other parts in here that don't imp[rove anything. In fact, if they are too large, they actually cause problems. I would hope they didn't enlarge the component holes on the PCB for these. Now, the darlington transistors they replaced are difficult to match, but they need to be matched. I would be concerned about this because there is normally no good reason to replace them unless they suffered in an amp blow up.

The input capacitors are already good film types. That and the RCA inputs are a make-work project. I'm not really happy to see these types of "upgrades" done, because they take away attention from what really needs to be done. Believe me when I say there is already enough to do without looking for stuff to replace.

The precision, low noise voltage shunt regulators that were originally installed are excellent. They shouldn't be replaced unless the leads are rotted right through. I get the feeling that this place simply replaces a bunch of parts. From looking at the web site, I don't get a great vibe from the place. It appears as though they pursue "upgrades" without doing the detail work required. I did not see enough test equipment to perform these repairs and "tuning" properly at all. I think that is what really sets off alarm bells in my head.

-Chris