ROTEL RB 956AX Voltage Conversion

[baoliver]

I recently purchased a ROTEL RB 956AX 110V. I would like to change its voltage to 220V. Could anybody help by giving me some tips or by sending me a service manual which probably will give me the instructions that I need? Thanks

[docfin]

Service manual for RB-956AX available here: http://service-manuals.webs.io

[TDWesty]

Originally posted by baoliver
I recently purchased a ROTEL RB 956AX 110V. I would like to change its voltage to 220V. Could anybody help by giving me some tips or by sending me a service manual which probably will give me the instructions that I need? Thanks

Rotel in North America will provide service manuals by email at no charge - I got one for my RCD-965BX CD last week.

I converted this unit from 220 to 110V without the manual -it's clearly marked on the transformer. Not sure if the amp would be the same though...

[Nrik]

Bought one Rotel RB-956AX used.
Two pairs of outputs were gone, and one speaker terminal was broken.
Got hold of the original transistors and fixed everything. It works great.

But:

The Idle current in all the outputs were set to 160mA. I think this is quite high for this amp so i re-adjusted it to 100mA.
I am suspecting the previous owner turned it up for lower distortion, but this could be why it burned the two outputs.

Does any one know what the Idle current is supposed to be?

[tazmc]

Nrik
were did u get hold of the transistors for the Rotel RB-956AX.
Need that and 2 resistors(big one) 1 chanel is gone.

[Nrik]

Tazmc

The original transistors are discontinued, so you have to look for NOS = New Old Stock

I was lucky that a small company in Copenhagen (not even email) had both drivers and outputs. You should try and call him, I am shure he can ship to Norway also.

A/S Telmo Elektronik.
Dronning Olgas Vej 24
2000 Frederiksberg
Telefon: +45 38103255

[Nrik]

...and check your driver-transistors before putting in new output transistors. If the drivers are gone too, the new outputs will blow again.

BTW: in another thread I was told that original bias should be about 45mA

[schro20]

I tried that web address posted earlier in this thread, but it appears not to be in place anymore. Does anyone have this manual on hand? or know where to download it? I just acquired this amp. Very nice indeed! But I am thinking that maybe a little restauration work is called for. A circuit diagram would obviously help... Any suggestions?

Thanks much!

Peter

[schro20]

I found the technical manual for RB-956ax at The Audio Circuit

Had to upload another to get it (they run some mutual exchange program, it seems).

Peter

[schro20]

I am back in the US and need to convert this baby to 110V. The circuit diagram shows the toroid to have a single primary with 4 taps. Only one of them is named with color in the diagram: white (the "bottom" tap). AC8 is currently connected to blue. The ordering of the wires coming off the toroid is white, orange, blue, brown.

I just put 118V (my local voltage) on the machine and took measurements against the white wire. Blue shows 118. Brown shows 123 (how can that be???) and orange shows 61. Looking at the ratios I want the orange wire to connect to AC8. That requires soldering. I am ok with soldering I am just surprised that this beast is built in such a way that soldering is required to switch voltages. They have terminals for all 4 wires. Its just that for different countries I guess the colors going to AC8 (active) AC7 (just a node on the circuit board with no connection anywhere and currently holding the orange wire) and AC9 (also no connection on the circuit board just holding the brown wire) would need to be changed. Weird.

So it looks like orange should be put on AC8 and then blue moved someplace else (I suppose I can put it on AC7). But is that what they really intended? Does anyone have a 110V version of this amp and wouldn't mind looking inside and checking (or maybe even posting a photo)? I would be most grateful.

peter