Rotel rack component wiring

[Donomite]

Ok fellows I need help because I don't want to mess up lol. Got a EQ, preamp and amp. The EQ has a line in and line out left and right connection. Would I go preamp output to EQ input then EQ output to amp input? Thanks

[stj]

Re: Rotel rack component wiring

yes.

[stj]

Re: Rotel rack component wiring

[Donomite]

Re: Rotel rack component wiring

Thanks stj. I actually got some info from the Internet and used the tape 1 monitor input and output. So I went preamp tape monitor out to EQ in, then EQ out to preamp tape monitor in. It's kind of confusing with all the selector switches on the preamp but I think it's Working.

[Donomite]

Re: Rotel rack component wiring

Ok guys I need help cross referencing components to mouser site. I have a transistor with open base to emitter. Number on part is A912 (R) 72. I think it's 72. I plan on replacing all caps in the preamp. The main issue with preamp is intermittent output to speakers. Removed preamp from loop and used EQ and amp. Works fine without preamp. This transistor came from the MC head amp & EQ amp circuit board. Thanks

[stj]

Re: Rotel rack component wiring

2sa912
https://duckduckgo.com/?q=2sa912&kp=...t-wt&kv=1&kh=1

[budm]

Re: Rotel rack component wiring

What is the model number of this Rotel preamp?

[Donomite]

Re: Rotel rack component wiring

what is the model number of this rotel preamp?

rc-2000

[budm]

Re: Rotel rack component wiring

Service manual.

[Donomite]

Re: Rotel rack component wiring

Service manual.

Thanks budm, I do have several copies of that manual that I printed last week. Is there a reason that the caps aren't listed on parts list. I know the cap info is on the schematics and actual cap. I have made a list if all can caps but am struggling with the mouser site. I will have to call them. I am excited to do the work but overwhelmed also lol. Thanks

[budm]

Re: Rotel rack component wiring

I use Panasonic FM to recap my NAD PRE-AMP.
https://www.badcaps.net/forum/showpo...2&postcount=65
Just type in the PANASONIC P/N of the cap you need into MOUSER search box.
You can also use what they call Audio Grade cap but I do not care to spend lots on money.
http://www.mouser.com/new/nichicon/Nichicon-Audio-Caps/
http://www.erseaudio.com/Products/Capacitors
http://tech.juaneda.com/en/articles/...apacitors.html

[Donomite]

Re: Rotel rack component wiring

I use Panasonic FM to recap my NAD PRE-AMP.
https://www.badcaps.net/forum/showpo...2&postcount=65
Just type in the PANASONIC P/N of the cap you need into MOUSER search box.
You can also use what they call Audio Grade cap but I do not care to spend lots on money.
http://www.mouser.com/new/nichicon/Nichicon-Audio-Caps/
http://www.erseaudio.com/Products/Capacitors
http://tech.juaneda.com/en/articles/...apacitors.html

Thanks a million...that's the kind of information I really needed. I can't wait to get some new caps in. Please stay tuned as I will be needing more guidance.

[budm]

Re: Rotel rack component wiring

That is a very nice looking pre-amp for 40+years products, I love old equipment.

[Donomite]

Re: Rotel rack component wiring

Happy New Years! I managed to get all caps for preamp in mouser basket. I really need help finding transistors on mouser site. For ex. 2SA912. I found some cross ref (BF435 & 2N3930). I can't figure out how to find a matching transistor on mouser. Help please!

[budm]

Re: Rotel rack component wiring

What is the transistor designator as shown in the diagram so we can see how it is being used?

[Donomite]

Re: Rotel rack component wiring

What is the transistor designator as shown in the diagram so we can see how it is being used?

Q136 on MC head amp /EQ board. The schematics are confusing..I wish it was as looking from the component side. I went ahead and placed order for the caps. I can order transistors from local supplier (Ralph's). Thanks!!

[budm]

Re: Rotel rack component wiring

Q136 is the output of the discrete OP-AMP circuit for the right channel only so it should not have affect of losing both channels.
When you use the sub, you have to use the NPN complementary pair to match the PNP. 2SA912 is complement to 2SC1885.
I buy form this place before.
http://audiolabga.com/mal_cart/mal_c..._button=Search

You can use 2SA1124 and 2SC2632
http://audiolabga.com/mal_cart/mal_c...0&find=2sa1124
http://audiolabga.com/mal_cart/mal_c...0&find=2SC2632

This one is also good for info:
http://alltransistors.com/transistor...ransistor=9039

You should also clean the switches and controls real well too, I use Deoxit.

[Donomite]

Re: Rotel rack component wiring

Q136 is the output of the discrete OP-AMP circuit for is for the right channel only so it should not have affect of losing both channels.

ok cool! As I remember...I first noticed the problem in just one speaker. I found another 912 with the same problem (Q139). This is so much fun! Oh I also got way ahead if myself and cut loose a lot of the wires rapped to post, especially on power supply. My plans are to solder back to post. I already practiced soldering to the post after lightly buffing them first with Dremel wire wheel. A lot if work ahead of me. Leaving to go offshore tomorrow for work for about four days. Will have Internet access though. Did I mention that I think I messed up the preamp by the way I hooked up the EQ. I used a tape 1 input but didn't loop it back out the tape 1 output.

[budm]

Re: Rotel rack component wiring

Use flux to help soldering works.

[budm]

Re: Rotel rack component wiring

You can hook up EQ or any sound processing devices (EQ, DYNAMIC Expander, etc) on the tape loop (this will allow to alter the sounds before feeding into the recorder if you want to) or between the preamp out power amp in for the stereo that has preamp out-power amp in, or between pre amp unit and the power amp unit.
You must sequence up the units properly to not introduce the thumb or pop into the speaker, typical sequence up is preamp, eq on first then power amp, on sequence down will be power amp off first, then eq, preamp. You do not want to damage your speakers especially if they are expensive.