As stated main fuse popped when plugged back in after having it unplugged for sometime. I looked it over very closely and everything looks good from what I can see. Anyone have any info on what to check and how to check transformer and rest of power supply with meter without running any power. Thanks for any advice.
I would start by disconnecting amp from its power supply.
Then check voltage across smoothing capacitors if turning it on doesn't blow fuse. Or even just check AC on transformer secondaries.
Then check voltage across smoothing capacitors if turning it on doesn't blow fuse. Or even just check AC on transformer secondaries.
Try lifting the fuses, that will disconnect the power amplifiers then work backwards towards the power in. After checking the transformers are OK.
Adcom GFA 535 has four 4A fast blow fuses on the two +/-50V rails powering the independent power amps. Lift them as suggested above and use a 40 W lamp trouble shooting assembly to determine if the power supplies are OK, and also to save future AC fuses from blowing; fuses are expensive. I faced a problem like this with a Radio Shack receiver. A power rectifier in its power supply [+/- 60V] was shorted and thus channeled AC from the secondary winding of the power transformer through the 8600 uF capacitor to ground; which was a dead short. If the 40 W bulb lights up, turn power off immediately as the power supply capacitor or other entity will/may get damaged.
BZ,
If this is the 535 and not 535II, send me a PM so I can send you a scan of the service manual. It will help.
If this is the 535 and not 535II, send me a PM so I can send you a scan of the service manual. It will help.
Thanks. I will try it tonight. I will post my findings. Hopefully it is something small and not the transformers.
the 40W light bulb is a very good suggestion. Build a Mains Bulb Tester.
If the bulb does turn on and stay on, then usually nothing gets damaged, not even the fuse/s. The bulb drops so much voltage that the mains input to the amplifier/transformer is down around 5 to 10Vac and the secondaries are down proportionately.
The Mains Bulb Tester lets you measure voltages around the transformer. But take care the system is still connected to LIVE.
If the bulb does turn on and stay on, then usually nothing gets damaged, not even the fuse/s. The bulb drops so much voltage that the mains input to the amplifier/transformer is down around 5 to 10Vac and the secondaries are down proportionately.
The Mains Bulb Tester lets you measure voltages around the transformer. But take care the system is still connected to LIVE.
Still blowing fuse . I'm going to have to start taking it apart piece by piece and check everything with back up power supplies. any in put will be good. Thank you.
Also some one said they posted a complete rebuild of one and I could not find it. That would be a big help. Thanks again................
Also some one said they posted a complete rebuild of one and I could not find it. That would be a big help. Thanks again................
I suggest repeatedly that every build should be checked for correct operation in stages via a Mains Bulb Tester.
Transformer power up alone is the FIRST STAGE.
Transformer power up alone is the FIRST STAGE.
Dim bulb tester is the tool needed. Then you start disconnecting power to different sections of the amp till the lite goes off. You've located the area of the problem and start checking components... However something that takes out a 4 amp fuse has to be a part that can pull 4 amps without burning up. Maybe with the dim bulb tester glowing you can feel what's running hot, disapating all that power....
You can measure voltages when the Bulb is lit. But the power going into the device is extremely low when lit (varies with the square of the primary voltage).
5Vac input instead of 115Vac input gives a maximum power that is only 0.2% of the rated maximum power.
It's the extremely low power if the bulb lights that gives the protection to the device.
5Vac input instead of 115Vac input gives a maximum power that is only 0.2% of the rated maximum power.
It's the extremely low power if the bulb lights that gives the protection to the device.
That is what I was going to do. I have to pick up a new bulb, fuses and other parts. Bulb was broke in my test rig. I'm just running short on time this month and have to go out to the West coast of Florida next week for a few days. Also have family coming to visit right after.
So when I last tried it with the other fuses pulled I think I heard one of the transformers buzz. I'm going to them test them hopefully this weekend. If it is the transformer can anyone recommend a replacement model part number and specs. I may have 2 that I can replace them with. I just have to find them and see if they are in spec with them. Thanks everyone for the advise. I have to much going on and I may send it to a guy I know in Texas if he has the time. Just the shipping is a killer. I think the amp is worth fixing.😀
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