Does anyone have VT150 schematic?

[calico88]

Does anyone has the Audio Research VT150 Schematic ?

is it using only 2x6550 ?

cal

[Zibi]

http://www.arcdb.ws/VT150/VT150.html

[showdown]

Looks like 4 x 6550 output tubes per channel, plus 2 x 6550 for the power supply.

[Zibi]

Exactly.

[wallruss]

hello, I need a schematic for a model VT150SE--can anyone help?

regards, paul crankbite@aol.com

[lazzer408]

VT130 (getting close)

http://www.mcmlv.org/Archive/HiFi/AR-VT130.pdf

http://www.arcdb.ws/VT130/VT130.html

[wallruss]

thanks for the VT 130 schematic--it does help a lot too, but the VT 150 has a different fully balanced driver comprising 4-12BH7 and plus and minus 360 volt DC power supplies.

I hope somebody out there has a VT 150 schematic to help me through this mess. (A cat napped on this nice warm amplilfier for a year until one day it quit due to a cat toilet event and I have had a hard time with it since then.) I have fixed 2 problems, but the DC drivers drift in a maddening way that a schematic would help with.

any tips appreciated---regards, paul

[lazzer408]

What exactly is happening? Maybe we could help you track down the problem based on only a handfull of facts. Such as, what is controlling the "DC drivers"?? How does that device detect and adjust for "drift"?? Voltage feedback loop?? So there's a simple loop to work around. (Just an example) Check the tubes pin by pin and verify the voltages are with-in spec. Perhapse a tube's tolerances are drifting as its temperature rises. Worst case scenario you'll have to track it down without schematics. I've had to do that many many times but with success. It's time consuming but you'll get by with a little help from your friends.

I searched for that schematic with every resource I could and found nothing. Have you contacted AR to see if they could email it to you?

Is the drive circuit like this one? http://www.arcdb.ws/D79/ARC_D79_schematic.gif

[wallruss]

It has 2 unmarked solid state TO 92 devices by each driver and the entire ampllifier is without any adjustments except for the bias for each 6550. I have only the one amplifier so I cannot check for unusual voltages. I suspect the TO 92 bias setting circuits but have no idea what goes on there. Audio Research was unfriendy and wanted to service it themselves.

[HollowState]

Originally Posted by wallruss

(A cat napped on this nice warm amplilfier for a year until one day it quit due to a cat toilet event and I have had a hard time with it since then.) I have fixed 2 problems, but the DC drivers drift in a maddening way that a schematic would help with.

If you haven't already done so, the circuit board and other internal areas that were contaminated need to be thoroughly cleaned. Urine is pretty conductive and corrosive. I would remove the board (if at all possible and making notes of all the wire connections) and wash it with rubbing alcohol and a tooth brush. Pay particular attention to any integrated circuits and the space between the leads, as welll as transistors and any high meg resistors. 70% rubbing (isopropyl) alcohol will not hurt the board or any plastic parts. Rinse very well with clean or distilled water and dry thoroughly. A hair blow drier helps with drying.

I suspect the VT150 uses a DC balancing feedback arrangement much like the VT130 does in the output to driver stage. Any contamination in this area would cause unstable drifting. I think a good thorough cleaning may solve your problem. I'm also a little surprised that AR refused a diagram. They usually will if you own their product. Maybe ask again and promise not to share it.