Resurrecting a Crest LA2210

[Courtec]

Yes i admit, i'm inspired by TomWaits and his excellent work on a Crown DC300A.
I'll get back to that....

But for now i picked up a Crest LA2210 amplifier. This amp has several problems. I don't even dare to switch it on as the silicon may create a meltdown in my workshop. After a quick scan:
- It consumed a lot of smoke from cigarettes. This means heavy cleaning
- the fan stopped working a long time ago and that gave heat!
- One pair of power transistors gave up and fortunately protected the rest.
- Recapping seems necessary, this amp is from 1991.
- I want 2 volume knobs on the front.
To be continued. See the first photo impressions.
Regards, "unable to keep clean hands Mr. Courtec."

[djk]

Crest LA1201

http://www.crestaudio.com/media/sche...matic_set1.pdf

[imix500]

Hi,
I wouldn't expect all that much from this amp once you get it up and running. I had a 601 in for a check up couple months ago at work. Upon load testing and checking THD+N it seems these amps are somewhat bandwidth-limited. The 601 was down -8dBV at 20K and -4dBV at 40
I would be very interested in how your amp measures if you were planning on doing it.

[Courtec]

First, thanks DJK for setting the model numbers in the right order. It must have been late last night... (oeps! stupid me. Is a moderator able to correct it?)

I think the 1201 is a well build amplifier. Rugged boards, good components and clever put together. Only the open chassis and the way it is cooled makes it necessary to keep it clean. How it sounds? Well, we'll see after i put this one back together.
And of course also measure some specs.
As you can see in the diagram it uses a amplifier STK3152MKIII module. A hybrid model with a discrete massive output board. Voltage +_85V and 300W output into 8 ohm.

First issue to solve: cleaning the boards. I start with the power board. The elco's must go. These are Philips models but 3 of them have a, to high, internal resistance. So i swap them all, 6800uf 100V. Here i must put in the euro's, the rest is not to expensive.

What is the best way to clean the boards? We'll i ran several options and ended up with a list:
1. Remove nicotine and dark brown dust.
2. It must be done wet, so remove critical components.
3. An aggressive cleaner is not the way to go.

I came up with a brush, warm water and a dish cleaner. Here in Holland known as Dreft but any soft dish cleaner will do i think. And it cleans! After cleaning i washed the board with demineralized water and used a hair dryer. The result is promising for the other boards as the pictures show.
Again to be continued....

[mrfeedback]

You can wash and scrub the boards, heatsinks, cabinet and front panel in a tub in warm water detergent solution and then immediately rinse and then blast with compressed air under all components and then heat well with hair dryer and then pace in warm environment (40+ *C) for 12-24 hours to ensure totally dry.
This is normal renovation treatment for amps that have lived in club environment.

Eric.