UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - REVOX A700 Transport Control and Capstanboard: Underdesigned transistors?

REDGUUZ · 28th Oct 2017, 11:08 pm

Sorry to report back rather late.
In the meantime I have overhauled the capstan, tapecontrol, relay and power supply boards to avoid that a faulty tantalum capacitor would wreck an unobtainable IC (TCA561, TDA1000 or SC10429).
I have also replaced the BC108B drivers (following the TCA561's) by BC141-16 's (as in the STUDER B67Mk1). It looks like the Tapacontrol board was already designed for these transistors.

wrt the noise issue of the TBA931 Op Amp's: On my deck all TBA931/2 's had already been replaced by TBA931/3 by a former owner/service technician (apparently in 1991).

BTW There is a chap in Germany offering a drop in replacement for the TBA931/3 using the OPA2134 OP Amp see:
https://www.ebay.de/itm/Ersatz-TBA93...item2807bbc016

Any comments on this replacement?

best regards, Martin

28th Oct 2017, 11:08 pm	#19
REDGUUZ Triode Join Date: May 2017 Location: Assen, Netherlands. Posts: 13	Re: REVOX A700 Transport Control and Capstanboard: Underdesigned transistors? Sorry to report back rather late. In the meantime I have overhauled the capstan, tapecontrol, relay and power supply boards to avoid that a faulty tantalum capacitor would wreck an unobtainable IC (TCA561, TDA1000 or SC10429). I have also replaced the BC108B drivers (following the TCA561's) by BC141-16 's (as in the STUDER B67Mk1). It looks like the Tapacontrol board was already designed for these transistors. wrt the noise issue of the TBA931 Op Amp's: On my deck all TBA931/2 's had already been replaced by TBA931/3 by a former owner/service technician (apparently in 1991). BTW There is a chap in Germany offering a drop in replacement for the TBA931/3 using the OPA2134 OP Amp see: https://www.ebay.de/itm/Ersatz-TBA93...item2807bbc016 Any comments on this replacement? best regards, Martin Attached Thumbnails