• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Balanced Audio Technology VK-D5SE

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Hi All, new here and looking to get some help troubleshooting a Tube CD player. I know it's not an amplifier, but I thought I would find more help here in tube amps than the digital cd realm. This is a BAT VK-D5SE tube CD player that uses 4 6H30 tubes for the output. One channel (2 tubes) works fine the other channel has a couple issues I think are related but maybe not. I do have the schematics, and before I go into gory detail and upload the schematics, I wanted to make sure I was in the right spot and could get some help?

Thanks a bunch
jim
 
Here goes. Left channel filament heats up fine, right channel filament seems to cycle for some reason. Each filament channel has its own voltage regulator, which is variable. They use the variable to ramp up to 6v. I did replace both, same issue. There is a relay on a separate circuit for the plate voltage. When this engages the plate voltage, it causes the right channel filament voltage to cycle, but not the left.

In standby mode, the player just heats the filament. In this case, both channels rise to 6v. But hit power to come off stand by and the above occurs. Now other issue is plate voltage on working channel is 150v. Plate on right channel is 130v, and the plate resistors are heating up on that channel. Not sure if this is a cause of that filament not being at 6v when the plate voltage kicks in? When the filament is cycling, it takes a long time to get back to 6v. In the meantime, the plate voltage kicks in.

I can upload schematics in the am. But that's the issue. I have replaced all electrolytic caps, both filament voltage regulators, and said relay. No help, same issues.

jim
 
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Ok, post at least the power supply and control circuit. Also, the theory of operation, if there is one.

Unless the filament circuit is ok, there's no telling what the tube is going to do, so the plate voltage can wait.
But by plate voltage, do you mean the power supply DC voltage, or the voltage on the actual plate of the tube?
 
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Here comes the schematics. Keep in mind, the schematics for left and right are one channel. Also, each channel has two tubes, schematic shows three but the cd player has a total of 4. They made one with 6 and one with 4, same schematic. This one has V1 & V3 and V4 and V6. Parts replaced are C34, C37, U8, U10, C26, C27, C30, C31, D8, D9. I have compared resistor values in circuit to the pin 1 on U8 and U10 (variable voltage regulators) and they are the same. Nothing in the filament circuit looks burnt, tested O2 and O3, same values. So the mystery is why does the left work fine and the right cycle. Also look at the relay which has been replaced = RL1. This is what, when it clicks, causes the filament to drop and restart on the right channel. I don't even see how this is possible. It's driving me mad, so if you have read this far, I'm offering a PayPal reward for anyone who finds the solution with me.
 

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  • out-left.pdf
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  • pwr.pdf
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  • control.pdf
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  • mute.pdf
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Ok, post at least the power supply and control circuit. Also, the theory of operation, if there is one.

Unless the filament circuit is ok, there's no telling what the tube is going to do, so the plate voltage can wait.
But by plate voltage, do you mean the power supply DC voltage, or the voltage on the actual plate of the tube?
Voltage on the actual plate of the tube. The left with good filament is 150v. The left with oddball filament is 130v on one side of the plate resistors and like 30v on the other side of the resistor, and they get hot in a few minutes and you have to shut it off.
 
Correct the right voltage regulator, U8. I did observe it's the Adj line moving as the input stays constant. With the adj line moving, that of course moves the output. Yeah, those two little 100uf 16v I did not do yet. Riddle me this though, why is RL1 causing this to cycle? And keep in mind when the unit is in standby I have a constant 6v, no movement. IF those little 100uf, 16v were bad, would if cause the issue all the time, even in standby???
 
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Joined 2011
Without a theory of operation in the manual, you'd have to take the time to figure out all of those details.
But since you've already replaced a bunch of parts, we can say that the C35 and C39 are much more
likely to be bad than any of those parts were, and to have developed excessive leakage after 20 years of use.
Do not substitute any other part for those capacitors. They must be low leakage types.

Digikey also has them, so do both channels. And there is free shipping, if you mail them a check with order for
the parts and your state sales tax (no credit card).
https://www.digikey.com/en/products/detail/nichicon/UKL1C101MPD1TD/4317967

6. Shipping Charges.
Products Shipping from DigiKey's Warehouse.
Except as otherwise provided on the Site,
shipping or freight charges and insurance will be paid by the customer*
* When a check or money order accompanies your order, DigiKey pays all shipping and insurance
(our choice for method of shipping) to all addresses in the U.S. and Canada.
 
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Its actually the same one. I've been driving myself nuts for weeks, so I had that already, just didn't think it was it, so I replaced the big ones first. Same thing with voltage regulators, matched them part number for part number (and RL2, same brand even). And through all this, it does the exact same thing. Plate kicks on left holds filament and goes to 150v on plate. Right, starts filament warm up very slowy from 1.5v to 6v but those plate resistors start to heat up.
 
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