...... one is blowing 3A slo-blo fuses instantly on powerup.
I've thought about trying a 4A fuse but ......
Sounds like a dead short. I would not increase the fuse size.
Take the amp to a repair shop.....
Possible problem could be a shorted electrolytic capacitor/s in the power supply.
Sounds like a bad 5AR4 rectifier tube. Order new rectifier tubes from Quicksilver. Might as well replace them all.
Did you call quicksilver? Sounds like a short as suggested previously. It may not be overt or another component which you can just swap out so easily. I assume you already changed the rectifier since it is tube rectified.
can you see any signs of leakage or stress to any of the electrolytic caps;I would agree with Jea48 that it could be a shorted capacitor in the power supply circuit.
Agreed on the rectifier tube or bad cap. Check for any caps leaking out material. I would bet it is a tube though. I have 3 pair of quicksilvers and never a bad cap. Jallen
Pull the rectifier tube out of it's socket, replace the fuse with the correct value then turn it on. If it blows again, instantly, you have a shorted power transformer.
It could also be a problem with the filament supply i.e. bridge rectifier, and not the high voltage supply. Hard to say without a circuit diagram.
I had the same problem years ago and it turned out it was a bad cable from preamp to amp.Try changing the cable,it just might be the problem.
Thanks for all your help and suggestions. I will try the preamp cable swap and try powering up without the rectifier tube before looking for a repair shop...
Hi, I pulled the rectifier tube out, inserted a 3A SB fuse, turned on power and the fuse did blow. How certain are you about the problem being a shorted power transformer? There is no visual indication (top or underside) of damage.
From a different standpoint, I had something similar happen with my 2 new VAC Statement monoblocks. Turned out that all fuses aren't necessarily the same. There is a greatly increased amount of current when an amp first turns on and if the fuse is not designed to accept this,it will blow most every time, regardless of its amperage rating. That's what happened to me when I got local Radio Shack slo blo fuses, as compared to the slo blo fuses VAC sent me.
My point is that before you go to any more trouble, just have Quicksilver send you some spare fuses for your amp. They will know which ones to send if you describe your situation. That would be the first thing I would have done. The other suggestions above are also helpful, but the easiest fix to try would probably be what I am suggesting. Good luck.
I repeat, you could have a bad rectifier in the filament supply.....
I agree with Hifigeek1, and a much higher probability than a transformer shorting.
To save some money, do you know anyone with basic electronics knowledge that owns a multimeter and soldering iron? They could measure the bridge rectifier, transformer, and anything else for shorting. Read the part numbers off any failed component, and order a replacement from many sources, excluding the transformer which would be available from the mfr.
Orrr, take it in for repair. Shouldn't be too costly unless a transformer.
I have a multimeter and a soldering iron but am a bit intimidated by a tube power amp...
Besides unplugging the amp, just make sure to bleed off all capacitors, if they are not already drained off with resistors across the +- posts/leads . Use an insulated handle screwdriver, or insulated wire with both ends pre-stripped 1/4", to short all capacitor leads just to be safe. That *will* resolve any "stored" shock potential.
I assume you know how to measure a bridge rectifier or discrete diodes, etc. If not, report back or google it. Very simple.
No, I guess I could short across the capacitor leads with a screwdriver but have no idea how to measure a bridge rectifier or discrete diodes. Does this require unsoldering?
Rawinsonde, do you have access to a digital camera - able to email 1-3 hi-rez pics of the amp's internal layout? If so, take some, view them for clarity, and I'll post a generic email address here to forward them unless you can link them here from, say: photobucket or similar.
I've tried searching for schematics, but to no avail.
Shorting across a power supply capacitor to discharge it is never a good idea. You can however use a 1K ohm 1watt resistor or greater wattage and bleed the voltage down.
Yes, I can take some pics of the . I'll go ahead with that...thanks I appreciate the help. I might be able to get a schematic. I'll try retrevo or other forums. I sure appreciate the help!
Rawinsonde, from reading a few internet forums, schematics are not available from Quicksilver, though reversed-engineered sketches might be circulating.
In any case, send your pictures to the email address below. I'll mark them up with instructions and email them back:
Thanks to all of you who posted help and suggestions. I may have found the culprit, a diode in the rectifier circuit reads shorted. I had to order a few of them online from radio shack. We'll see in a few days if that fixes it...
In addition to all of your helpful posts, I would like to especially thank Frank (Metro04) who spent a lot of time with me in detail checks and troubleshooting. Without that help, I think I would still be down as there are no service outlets available here for the product.
was it in the filament supply????
Thank you Ray (Rawinsonde). It was a pleasure and glad you're back to enjoying them again.
For those interested, these amps have hybrid rectification for the high voltage supply which consists of a single 5AR4 tube and two diodes configured as a "bridge" rectifier. The two diodes were shorted, thus shorting the transformer's HV winding to cause the fuse to blow. The filament supply is exclusively A.C.
Ray had a multimeter, took various measurements, bought replacements from Radioshack, soldered them in, done, except....... now the other channel no longer worked.
Ray performed systematic troubleshooting and found that his other amp was the culprit with a non-functioning rectifier tube - possibly caused when swapping tubes into the shorted amp early on. He had several used 5AR4's on-hand, measured them initially for shorts (one was), then tried the remainder in the amp until one yielded a working amp (two did not).
Well done, Ray!