C Audio Pulse 2x 1100 watt amp

Looks like all 4 off 1M , need replacing, all those matching operational position of R182. Has 80 V in normal use over 1/3W 1Meg and used in dampish conditions is enough to make it go high or even o/c., not removed it yet. In an area of circuit not easy to measure or even compare ch for ch. Hooking another 1M across it is enough to give amp operation without disabling the DCsense error protection. Its this R that takes the central biasing section low at power up before the Tr25+C53 section becomes operational.

You're a braver man that I am Mr Cook. I've seen 2 of these and decided on both occasions not to touch it with a barge pole.

Perhaps that's a sign of getting older and wiser. - some jobs you really do need to refuse for your own personal well being.

Good luck,

Gareth.

Don't know about you, but I'm finding more and more that these big power amps are not worth repairing, due to the low cost of replacements. The shop that I do a lot of work for will often tell me not to spend more than half an hour making sure that it's not a really simple problem, as a replacement can be had for a couple of hundred quid or less. Suits me just fine as I still get an examination fee, without the thought of all the potential grief of replacing a bunch of output transistors, and trying to ensure that it doesn't all go bang again when you've finished. As you say, perhaps a case of getting older and wiser. Not so many years back, I was up for any repair, just for the challenge of not being defeated. These days, it's about making a living, and if a repair does defeat me, it's just san fairy ann and on to the next one ...

Arfa

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At least the schema are around. Some notes in passing, you have to be careful how you pick up that large pcb , by the heatsinks and front metalwork not by the edge or rear as those large piercings make it weak. Discharging the rectified mains DC cap of course. Maybe all component oles( certainly the 4 off 1Meg Rs) are the size for power transistor legs or IC-pin eyelets so although plated through holes , minor components like 1/3W Rs have a lot of solder around the leads so libility to cracking I would think.

Not actually the 1meg failed it was the TO92 over the complementary 1meg gone 35uA leaky, pulling the zero point upwards

So, how did your lead-free lecture turn out last week ? Well received ? Did you video it ?

Arfa

Did

outline from the .ppt here

And someone else from gas-fitting, no problem there as such, they just charge the customers £250 for a new controller board when it is just PbF solder failings on the not so old previous board, subjected to normal in-service conditions but too much heat for pbf.

Arrrrgggg!

I just repaired a 600 watt Coolmax PC PSU that had defective PBf soldering. Don't -ever- buy that brand, they are very poorly assembled.

"N_Cook" wrote in message news:i2bfro$df7$ snipped-for-privacy@news.eternal-september.org...

Yes, I've come across this one. Apparently, there's quite a lot of problems caused on these PbF boards, by relay hammer, which leads to the joints on those devices fracturing. The real bummer on this though, is that the boards have been manufactured in lead-free to help the environment (according to the green mist eco-bollox brigade, anyway) but what's actually happening is the things are failing *because* of the lead-free solder, and then a perfectly otherwise serviceable board, which could easily be repaired, is being replaced as a service spare, much like a faulty gas valve or pump motor or whatever, because the person who calls out to fix the fault is a plumber, and has little or no electronic savvy. A person who I know that is a plumber, says that his garage is full of scrap boards, and that every now and then, he just collects them all up and takes them to the tip. How green and eco friendly is that ? I've been trying to persuade him to collect a big bag of them up for me to take off his hands, but no luck so far ... I wonder if the control boards from other appliances like washing machines and dishwashers suffer the same because of lead-free construction. Actually there is a little domestic electrical sales and repair shop next to one of our cafes. Next time I'm down there, I will pop in and see the owner and ask him. There might be some mileage in this. I'm thinking purely from the business angle and wads in my pocket of course, rather than the green issues ... :-)

Arfa

Have you repaired the amp yet? I sent you a couple of off list messages but they bounced. I have repaired a few of this type of amplifier and may be able to help troubleshoot it. Contact me off list at IFixAudio at GMail.com.

Jim

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No valid emails used on usenet The one with leaky TO92 repaired and waiting for owner to return from holiday. Second one initially looked at , problems again in a TO02 device in a different area of one amp, gone B-C-E shorted so more obvious a problem. Waiting for owner to return before progressing on that one. Third one not looked at other than also goes into protect and no obvious problems with the TO3s , perhaps so well protected that rarely do the YO3s get a chance to fail.

I will use a valid email account to contact you