I have a buddy who lives many miles from me who is having problems with a pair of Adcom GFA535 amplifiers after an electrical storm. He took them to a local (to him) repair place and was told that the primaries on both are opened. I'm sceptical, since the favorite buzzword of a clueless or lazy tech is 'bad transformer'.
Is there anything in the primary of a 535 that might make it appear that the transformer is bad (soft-start, NTC thermistor...)? If it appears that the transformers are indeed bad, are the voltages from the transformer close to a standard that might make them easy to replace with an aftermarker transformer?
Thanks guys!
Is there anything in the primary of a 535 that might make it appear that the transformer is bad (soft-start, NTC thermistor...)? If it appears that the transformers are indeed bad, are the voltages from the transformer close to a standard that might make them easy to replace with an aftermarker transformer?
Thanks guys!
Hi EchoWars,
I'd be surprised to see an electrical storm take out the transformer. The shop may have killed them by shorting the fuse and turning them on. I'd be taking them back in a hurry. Measure the primary to see if they are open (thermal fuse gone). You may be able to replace those (takes some skill and luck).
May just be a shorted rectfier or output. Some repair guys aren't to swift. (I'm a repair guy, I've seen so much destruction at the hands of other techs). TIM - technician induced malfunction.
-Chris
I'd be surprised to see an electrical storm take out the transformer. The shop may have killed them by shorting the fuse and turning them on. I'd be taking them back in a hurry. Measure the primary to see if they are open (thermal fuse gone). You may be able to replace those (takes some skill and luck).
May just be a shorted rectfier or output. Some repair guys aren't to swift. (I'm a repair guy, I've seen so much destruction at the hands of other techs). TIM - technician induced malfunction.
-Chris
Fair enough. You are suggesting that the transformer has a thermal fuse in there somewhere?
You wouldn't happen to know the transformer secondary voltages are?
You wouldn't happen to know the transformer secondary voltages are?
I was going to say don't be so quick to judge an unknown repair shop, but then I thought of some my stories (I've been out of the biz for 8 years now - 'the good ol'days'). In general I'd have to say for the amount of knowledge and skills needed to be really good it is almost as badly paid as teaching (my new profession).
But back to the topic: I can imagine lightning taking out a transformer, of course I would expect many other electrical things in the house to be also damaged.
Thermal fuses in xformers - I know why they are there but why not make them easily replaceable? Seemed such waste to have to throw out a large lump for the sake of a cheap fuse. I did repair some, and a few had extra terminals which you bridge and check if everything else was OK - of course with lawyers and all I was not about to bypass the thermal fuse.
If you can replace it careful with that soldering iron ...
But back to the topic: I can imagine lightning taking out a transformer, of course I would expect many other electrical things in the house to be also damaged.
Thermal fuses in xformers - I know why they are there but why not make them easily replaceable? Seemed such waste to have to throw out a large lump for the sake of a cheap fuse. I did repair some, and a few had extra terminals which you bridge and check if everything else was OK - of course with lawyers and all I was not about to bypass the thermal fuse.
If you can replace it careful with that soldering iron ...
Member
Joined 2002
Hi EchoWars,
Yes there is a fuse in there, can't remember what the secondaries are. I did get some thermal fuses from Nakamichi years ago ... or was it Adcom. Can't remember. I do recall changing them.
My point was, confirm the fault first. Go from there. Any time I've seen lightning take someting out, that something was usually a semiconductor or few (and tubes - wow). Power transformers normally survive. They are tough critters.
-Chris
Yes there is a fuse in there, can't remember what the secondaries are. I did get some thermal fuses from Nakamichi years ago ... or was it Adcom. Can't remember. I do recall changing them.
My point was, confirm the fault first. Go from there. Any time I've seen lightning take someting out, that something was usually a semiconductor or few (and tubes - wow). Power transformers normally survive. They are tough critters.
-Chris
Member
Joined 2002
anatech said:
I agree the reason i asked about the kind of tranny was to help you locate the fuse and get it apart. Trannys are really strong devices. I saw a carver trany die due to max load max power running and the speakers shorted out and well the amp was a paper weight : O )
It's been a long time since I've worked on a 535, but I do remember that a few Adcom units had MOVs, (though they were usually preamps or sources). If the 535 has them, then they would be small bright blue epoxy capacitors, most likely on the PS board.
I've also had to replace a couple of 535 xfmrs, bur never both at the same time.
FWIW - Even though the 535 is rated at 60WPC, it really goes to 80WPC PS sag included!
Good luck!
I've also had to replace a couple of 535 xfmrs, bur never both at the same time.
FWIW - Even though the 535 is rated at 60WPC, it really goes to 80WPC PS sag included!
Good luck!
djk...thank you!!
No toroids on the 535? And I assume that it uses a single transformer and power supply to power both channels? No, the unit isn't here, and I don't think I've ever seen the inside of a 535.
No toroids on the 535? And I assume that it uses a single transformer and power supply to power both channels? No, the unit isn't here, and I don't think I've ever seen the inside of a 535.
The little 535 is the only true dual mono power amp adcom made ;-)
It had 2 E+I trafos, rest had single toroids.
It had 2 E+I trafos, rest had single toroids.
EchoWars,
I think the truth about the failure will come out once you see this fella. The fuses aren't too bad to change on most EI cores - if you need them.
-Chris
I think the truth about the failure will come out once you see this fella. The fuses aren't too bad to change on most EI cores - if you need them.
-Chris
No, it has two little square jobs.
The GFA545 had a single torroid running about ±55V, and one more pair of outputs.
If you look you will see the PC board and the sink on the GFA535 are laid out for the extra parts.
I think you would have a hard time retro-fitting a torroid into the GFA535 chassis though.
ECG used to sell one-shot thermal fuses in a whole range of temperatures. If I replaced them I always went the next LOWER temperature as the transformer insulation was stressed from the first time they went.
If the customer blew them more than once I told him to buy something else.
The GFA545 had a single torroid running about ±55V, and one more pair of outputs.
If you look you will see the PC board and the sink on the GFA535 are laid out for the extra parts.
I think you would have a hard time retro-fitting a torroid into the GFA535 chassis though.
ECG used to sell one-shot thermal fuses in a whole range of temperatures. If I replaced them I always went the next LOWER temperature as the transformer insulation was stressed from the first time they went.
If the customer blew them more than once I told him to buy something else.
NTE still sells the thermal fuses in a nice range of temps. I'd just have to decide what might be appropriate...if that is the problem.
Just look up the value in your area. In Canada we had a 10°C lower limit than the States. We changed transformers by the box. I remember that Yamaha was hit hard by this (nothing wrong with the xformer, just the fuse). I would tend to install the same temperature as the original.
-Chris
-Chris
I have no idea what a temp of a thermal fuse internal to a transformer ought to be. What did you use? That would at least give me a ballpark figure to work from...
Hi EchoWars,
Now that was a long time ago. Look up the requirements in UL. You can't go wrong there. Canadian standards would have no bearing there, although they are supposed to be unified by now.
-Chris
Now that was a long time ago. Look up the requirements in UL. You can't go wrong there. Canadian standards would have no bearing there, although they are supposed to be unified by now.
-Chris
I'll preface this with: 'Ive never had to repair an Adcom xformer'.
In the xformers I could/did repair the fuse had markings and I would just replace with the appropriate part. So if you can get to it it should be no problem, some fuses were buried and unrepairable.
Bill
In the xformers I could/did repair the fuse had markings and I would just replace with the appropriate part. So if you can get to it it should be no problem, some fuses were buried and unrepairable.
Bill
Appears that UL will show me its requirements for the small fee of about $215 so I can download a pdf.
I don't think so...
I'll see if the fuse is the problem first, then decide what to replace it with.
On the 555ii's if I remember, the thermal breaker could be bypasses as it has a separate cable. i.e. you could connect the primaries with or without having to go via he fuse/ breaker. I think it was the brown wire...
If the have schematics of the 535, perhaps you can rig it from the outside...
If the have schematics of the 535, perhaps you can rig it from the outside...
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