Good Afternoon Gentlemen,

I am not sure if this piece of equipment is vintage enough to post here, but I am out of sources. If someone could recommend a more suitable site then I would try there! In the interim, here goes!

Bought the unit on eBay...description said problem with B+...so I knew it needed some attention. Turns out that when I got it many things did not work, principally the DVM. When set to BIAS VOLTS, I get some -8.8 to +17 over the range. The output on the jacks is 0 to 30 VDC as it is supposed to be.

Anyone know what common faults with this unit are or where I could go on the Web to find assistance?

Thanks for your time,

Mitch

You might want to compare the metering circuit to that in the VA62 - which also has a similar bias supply. I fixed an "unfixable" VA62 simply by swapping the A-D converter chip around in the socket (it was put in backwards by the previous tech that deemed it "unfixable")

Sencore wasn't likely to design a different metering circuit for each or their products, so most likely, the VA62 and TVA92 are alike. Phil Nelson has a VA62 and may be able to provide some help.

IIRC, the VA62 meter circuit has some input protection diodes - I've seen them go bad as well. The SC61 meter also has the diodes that go bad - perhaps they duplicated this as well in your TVA92?

Wish I could be of more help - I've only played with a TVA92 at a Sencore Sales Presentation/Tech Training Seminar. Bitching Unit - sub the complete horizontal/sweep section of a TV (sans IHVT)!! That and their LCR meters impressed me the most.

Cheers,

Hi Brian,

Thanks for the response. I will have to look for a schematic for the VA62 to check out the meter section. Any ideas where I might find one?

Hopefully there will be some similarities between them, but the VTA91 is an electro-mechanical nightmare with a lot of microcontroller controlled relays switching sources and attenuation, and relays always make me worry! There are also many opto-isolators used to keep high voltages away from sensitive digital lines! Quite a troubleshooting adventure! I'll keep everyone in the group informed as to how things go!

I will also check out the diodes, thanks for the tip!


Any ideas if there is a Sencore repair group/forum around on the web? Hopefully this will be a common fault and someone can point me in the right direction! I' hoping!!

Thanks again for your response,

Mitch