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-   -   Arcam A85/90 fit for purpose? (https://www.diyaudio.com/forums/solid-state/324083-arcam-a85-90-fit-purpose.html)

friendly1uk 19th June 2018 12:52 PM

Arcam A85/90 fit for purpose?
 
I quite fancied an A85 but they're all broke? Today on eBay, both 85s and 90s are listed, but only broke. I have been watching a while. It seems about half of them have failed. Many are sold just as power amps as it seems it's issues with input selection that's most common. Almost a theme. Such that you could argue that under the sale of goods act, Arcam have fouled.



Has anyone got the drawings, or hands on experience from fixing these things? I'm obviously concerned that anything I buy will be broke within the year. So I'm interested in whats been used, as I have to expect very limited life from one now. If it's not off the shelf parts, I need to start my 10 year long process of amp choosing, all over again.



I have found similar posts on other forums, but no answers. Though drawings were shared privately, ending the discussions.

Mooly 19th June 2018 12:57 PM

HiFi Engine have the A85 manual I believe.

JonSnell Electronic 19th June 2018 01:05 PM

They have a digital switch for selecting inputs and rarely fail. Check the 5v supply to the uProcessor.

friendly1uk 19th June 2018 01:28 PM

I don't actually have one Jon, I'm just quaking at the thought of owning one. I want it... but the number of broken one's is truly outstanding. I thought perhaps they had used something like a micro controller, running their own logic. If that makes sense.





I will have a look Mooly. Thank you.

friendly1uk 19th June 2018 01:45 PM

Well that's that then. A microprocessor with 100 legs. I will keep my Alpha 8r

RM 19th June 2018 02:19 PM

As I used to repair these in Norway way back I still have complete motherboards, inputboards and even frontboards for A85. All new and unused.

Maybe also 1-2 RIAA upgrade kits for A85

Also several mainboards for CD players, including DAC boards.

3-4 unused channels for the P1000, 2-4 transformers, and even new Controlboard for same.

Regards
RMalmin

jaycee 19th June 2018 02:32 PM

The microcontroller is extremely unlikely to fail in itself, and is likely not the cause of the failure of the units youre seeing.

Define "not working". There's probably a lot of dicks blowing them up with party usage, putting a bigger fuse in to "get it working" and causing further damage in the process.

The amp does use the SAP15 output transistor, which is known to suffer from blown emitter resistors if pushed too hard. The STD03 + external emitter resistor could easily be fitted if this was a problem.

RM 19th June 2018 02:47 PM

One major problem with the front boards were the socket for the flat cable going to the input board. It was a bit on the "soft" side and would "bulge" out in the middle section causing the wires in the center of the cable to loose contact. Either change the socket, or easier; insert a little piece of plastic between the cable and socket. Maybe only 0,5 mm thick?

Regards
RMalmin

friendly1uk 19th June 2018 10:14 PM

Hi RM. I bet you have PM's for these upgrade boards already :) It's very interesting to hear about this plug. Perhaps thermal cycling is the cause of quite a few failures.


Jaycee, it's always front end. Many are sold as power amp only.

RM 19th June 2018 11:14 PM

This particular problem`s root were solely due to a low quality connector.

You are correct, first come - first served.

RMalmin


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