Hi Luke,
I just pulled a 522B board from my stock and have it siiting on my desk in front of my monitor. When I finish what I'm doing I'll take care of it. Thanks for the reminder again.
Mike
Hi Luke,
Remove the cap and resistor, replace 10 meg with 15K and install a 1K to ground as shown. This removes the return from the tone controls and provide a resistive feedback network whose gain matches the tone control networks.
Sorry it took so long for something so simple.
Mike
Remove the cap and resistor, replace 10 meg with 15K and install a 1K to ground as shown. This removes the return from the tone controls and provide a resistive feedback network whose gain matches the tone control networks.
Sorry it took so long for something so simple.
Mike
Attachments
I'm pretty sure the relay grounds the output until time in, could be as simple as dirty relay contacts not grounding the output. The relay is on a plug-in board, remove the board, remove the relay cover, clean the contacts with a piece of paper soaked with DeOxit or similar, and the put it all back together. A new relay would be nice but not sure if those are available now.
Did you get answers to your previous request on the line stage alignment?
Craig
Did you get answers to your previous request on the line stage alignment?
Craig
Well that sucks. The other type of relay, which I have in front of me now, is a NF2E-12V which has a removable cover. The pin out is different so that will have to be sorted out if you can find one. Or try looking for one of the EDS relays. Until then make sure you turn your Thoebe on first, wait a few, then turn the amp on.
I think my Thaedra I has an EDS relay I'll see what I can dig up.
Craig
I think my Thaedra I has an EDS relay I'll see what I can dig up.
Craig
My relay board is a 528C and it's out of a Thaedra II. All 500 series numbers are originally Thoebe numbers, which I think was the 5th in the GAS lineup. The original Ampzilla was 100 series, the Thaedra I was 200 series, etc.
My Thaedra I has a MEKO 55-2125-30 plug in relay, so maybe that will work in the Thoebe.
The big resistor next to the relay changed with the type relay also.
Craig
My Thaedra I has a MEKO 55-2125-30 plug in relay, so maybe that will work in the Thoebe.
The big resistor next to the relay changed with the type relay also.
Craig
I'm attempting to set the phono card (523B)on my Thoebe, but cannot get 1.5V across R301(R358). R301 has ~2.5v across it and does not change with adjustment to R366. I can only get 1.2V across R356, adjusting R365 does have an affect. I can adjust test point (TP) at R349 to ~0V via R304, but TP at R309 stays steady at 8V. I pulled the card and have 27V+ and- so I believe the main board is ok. I swapped out the IC MC1458 for a new one but no change. Any Ideas as to what to check next? Thanks.
Craig
Craig
I'm looking at the Phono Circuit (Thoebe, Thaedra) dated 7/25/77 and there are mistakes. Both the DC balance and idle current adjust pots are both labeled as R366(365), is this what you see on your schematic? The adjustment in the bottom left corner is for DC balance and the adjustment in the middle of the schematic is for idle current. I don't have this particular board in my Thaedra, I or II so can't help you much.
Craig
Craig
llwhtt,
Thank you for looking. I have the same schematic. I can follow the traces to get to the correct potentiometer. I’d like to verify R301 (R358) are to have voltage adjusted to 1.5v across them and not D301(D310) as called out in a setup procedure for board #523 that I have. The procedure I have also adjusts R363(R364) (two center pots) to obtain minimum reading across R309(R349). Again thank you for your time.
Craig
Thank you for looking. I have the same schematic. I can follow the traces to get to the correct potentiometer. I’d like to verify R301 (R358) are to have voltage adjusted to 1.5v across them and not D301(D310) as called out in a setup procedure for board #523 that I have. The procedure I have also adjusts R363(R364) (two center pots) to obtain minimum reading across R309(R349). Again thank you for your time.
Craig
