tti tg315 service manual?

[vixo]

I picked up a cheap, new TTI TG315 on ebay. Unfortunately the DC offset isn't calibrated properly which is annoying.. looking inside there are a fair few trim pots but nothing on the pcb is labelled. Does anyone have a service manual or could give me any tips on finding one? I don't want to start twiddling pots randomly...

[glarsson]

Have you tried the obvious option; ask TTI? They are usually very nice and will send what they have available.

[vixo]

I have sent them a message at aimtti.us. No reply yet - thought i'd ask on here in the meantime

[bd139]

Compare with the TG200 series manual. I think they have the same or very similar boards in them. Just a different case and counter arrangement. The design has been around forever.

DC cal on these usually calls for a DMM 4.5 digit or better, connect it across two pins in the DC summing amp and adjust the trimmer until there is a null reading. If you can find the summing amp and pot you can do this without the service manual. Basically you’re trimming the offset of the op amp.

[vixo]

thanks! good shout on the TG200 series manual. I'll have a look and a rummage..