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Hi,
I pulled out my old BAT VK-5SE preamp and set it up recently. It is dual mono design. It sounds fine. But I noticed that one side of the transformer is much much hotter than the other. Any clue for me to check?
Thank you.
Follow Ups:
Unplug all the cables....especially the one from the wall, and don't replug anything until you get it back from BAT.
nt.
But unfortunately the preamp didn't arrive intact after shipping. Many years ago, the original two 6-pak oil output capacitors were leaked. I took out the pack and replaced them with 6 X Russian oil caps using hot glue gun to glue the 6 caps together. The amp and caps were working fine. But during this transportation, the hot glue cannot held 2 X 6 output caps and fell off. Victor's staff saw the many loosen and felt off capacitors inside the preamp, they said the preamp is beyond salvage and cannot be repaired. I was dismay, but when I looked at the picture they send me, it was just output capacitors felt off. I told Victor to take a second look, all of the capacitors are just output caps loosen off. But I didn't get respond from Victor yet.
NOT working on modified BAT gear that was not done by BAT. Keep trying to contact Victor.
Also did you let Victor know before you sent it to him that you had messed with the preamp and changed the caps? I don't remember you mentioning that here to us when you first posted your thread. What else have you done to the BAT preamp? I have a feeling there may be more to this than just the caps being replaced. maybe when the caps came off they ripped up the pads/island for the through holes from the traces. That will be a lot of time and rework to repair traces and pads, I know this from experience of repairing that stuff.
Victor has a certain way of mounting those 6pac caps so that doesn't happen. So there may be just too much damage done when the caps came off.
So without seeing the pic, I can't tell you how bad it actually is. Some things a Technician hates to do besides tracking down an intermittent failures is trying to repair some gear that has been tampered/messed with. It's a lot of work to try to figure out what was done and try to undo the changes to get it back to working order how it came from the factory.
I know Counterpoint would not even look at a piece of their gear if it was modified or tweaked by someone else.
Hopefully they will reconsider and repair it but IF they do repair it, it will most likely go back to original status and will cost you! but it may not be worth their time and too much money.
I didn't change anything except those 6pac caps. 3 years ago, it had pop sound when I switched the mute switch. I emailed Victor and he told me its caused by the leaking 6pac. That's the only thing I changed.
My preamp would pop when the mute button was pushed. So it only has the caps replaced in your preamp?
Since the caps came off in shipping, I'm sure there is damaged traces and pads.
If BAT deems it beyond repair, have it shipped back and look for a local tech willing to try and repair the traces and pads. Hopefully the tech is good at repairing traces because it can get tricky. Then have him go after what is causing the transformer to get hot.
Since I was looking at pics of the inside of the BAT VK-5SE, looks like the Dual transformers have the filament winding inside them as well. Mine has a separate transformer for the filament PS along with the two transformers for the B+, so you may have a heater PS problem.
OP-
can we get an update?
Swapping tubes channel to channel is a good suggestion. If you like tools/toys, infrared thermometer is a good one. If it is a leaky capacitor, it will also be heating up. AC clamp current meter, another good toy/tool. Clamp on the transformer feed and you can measure current difference as you experiment with swapping tubes.
I switched out all tubes, but problem still exists. If it is leaky capacitors, will I smell anything or see deformed?
I see none of that, it is better to start on checking those transistor regulators?
Electrically leaking, should be getting warm, might deform or change color of circuit board. I can't believe i'm suggesting Harbor Freight, but they sell an infrared thermometer for $35, probably less with their screwball coupons.
http://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-60725.html
If I remember correctly Fluke bought the company that first made them. I have one of those, find all kinds of uses for it. And for the problem you are describing, since you can compare temps against the other channel, should be helpful.
Consult Victor.
Weird, because Victor is VERY easy to get in touch with.
I contacted Victor, and he suggested to ship it for service. I hesitate to ship it back and fro. I see that is the last resort. Therefore I ask advice here first to see whether I can fix it myself.
i have sent gear back and forth to BAT multiple times without any issues. This has always been for upgrades or retubes (when i thought i had a problem).
Victor has always been really helpful both by email and phone he has kindly guided me through a couple at home troubleshooting and replacements (ie replacing an vk55 switch, checking tubes on the old vk60).
In general, if he recommends sending something and it's probably reasonable.
it seems like you have checked all the ysual suspects.
good luck,
No you can't fix it yourself. It will be money well spent to send it back to BAT rather than ruin a high end piece of equipment.
This is why I told him a while back to contact Victor and to send it back to BAT.
Just being honest but if your technical experience is that limited then trying to find a voltage regulator problem is far above your level. Besides there are other IC in there that will be blown if you do things wrong.
Ship it.
I wouldn't mess with it since it is High Voltage. Just contact Victor at BAT to send it back for repair and a thorough check up while it's there.
I recently had an issue with one of the Filament supplies in my BAT VK30 preamp. It had a bad voltage regulator.
If it doesn't follow switching tubes then yes, it is a component.Heck, I had a preamp that out of the blue would blow a voltage regulator like clock work. You could mark it on a calendar.
At that time I was heavily into NIB NOS vintage (rare$$$) 12AX7 tubes and this regulator would take them out. A rare tube that sat in a box for 60 years trashed because of a crappy thirty cent part.
try the tube thing and unplug all connections.
charles
Edits: 07/13/16
but still the same.
There is not obvious burn on anything I can see. Yes, I do smell a little bit something, but not strong, and don't know where it came from.
I only switched rectifier tubes, do I need to switch other tubes to test? I am a bit nervous to power it up, I am afraid to damage more related components.
Any more suggestion?
Stupid question but how does it sound?
Any tubes glowing?
I do think you need it serviced. Just from looking at the pictures it doesn't look like the kind of piece you want to learn on how to fix.
It is not the causes. It don't see capacitors' deform or smell anything. It is better to start at checking those transistor regulators?
If it was a regulator you would be a strong low hum.
Again does it actually play music well?
If it really is dual mono and warmer then DO have it checked before something bigger goes.
charles
try switching ALL the tubes to the other side. See if the heat follows the tubes.
Also look for any discolored or deformed capacitors or toasty resistors.
Is it possible that one or more capacitors shorted that causes the problem. Actually the transformer was very hot, even after a couple seconds of ON.
I'd either wait for Victor to reply, or just keep your hands off the warmer of the two transformers & perhaps take MC Hammer's advice...
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