Bush Arena RA3700 schematic? - UK Vintage Radio Repair and Restoration Discussion Forum

ekjdm14 · 2nd Mar 2019, 5:11 pm

Just wondering if anyone has, or knows of a source for, a service manual or schematic for a Bush Arena (Rank) RA3700 model stereogram? Have looked in the usual places and no mention of the system, only other reference to the model I could find was one for sale on that auction site but otherwise have drawn a blank.

I've just picked one up from auction and, as well as the usual servicing of the Garrard SP25 MkIII turntable, it has very low output on the right channel & would appear to be a failing within the balance control circuit or perhaps the stereo/mono selector since output on the left channel remains high even when swinging the balance control. "buzz test" on the cartridge wires produces a loud response from both positive wires but only on the left channel, the right again is very low. This is with the selector in stereo or mono.

(The balance pot on initial looks seems to be working, and indeed right channel output does increase marginally when swung all the way over, but without any significant cut in the left channel.

Failing a schematic (it doesn't look that complicated of a circuit in all honesty) any suggestions as to what could cause this kind of thing would be much appreciated.

Thanks, Dan.

teetoon · 2nd Mar 2019, 8:20 pm

Hi Dan. The amplifier section is the A220 as in this recent post with a very useful schematic.https://www.vintage-radio.net/forum/...d.php?t=153781
Hope this helps.

David.

ekjdm14 · 2nd Mar 2019, 9:29 pm

Thank you for the link, the schematic seems to largely tally although the outputs are a different type but it's certainly similar enough to be a great help in tracing where things go/where they ought to go.

Thanks very much.

Big jim · 3rd Mar 2019, 7:11 am

Sorry I don't have the circuit .but I'll put money on it being faulty 10mfd capacitors in the signal path the little gray ones

ekjdm14 · 5th Mar 2019, 10:49 pm

The circuit is largely similar to the one linked in the thread above, I've made a start checking things while I had a few minutes earlier and the 250uF caps in the RIAA preamp were certainly iffy, I had a couple of usable pulls that have been fitted in their place, the 10uF on the RIAA seemed to check out but looking at the schematic and given your comment above I will likely have to buy a quantity of 10uF anyway so may replace them when I do the others.

Next job is to start checking the caps on the main PCB. Thanks again for the links & suggestions.

ekjdm14 · 23rd Mar 2019, 8:39 pm

Further to this thread (the RA3700 has been relegated to the rountuit pile for now), I now also have a model BS3049C (AudioSystem 1500) music centre. It's a lot different to the A220 circuit and has quite a few IC's on board. Still a fairly modular design but a lot "busier" inside & with a rough date from the latest IC of about 1978.

I can find reference to only one other so far online, to do with the turntable and that ended not-so-well, with the whole thing drenched in WD40

I hardly need a schematic for the symptom I have (no output on one channel, just humming & the other channel working reasonably) but it'd be nice to have one handy in case I find other issues as well.

ekjdm14 · 23rd Mar 2019, 9:12 pm

Indeed, one dead 220uF/25v cap on the amplifier board later and we have the Rock Show blasting out Feeder on both channels & in glorious stereo.

I have to wonder who Al is though, and why he/she felt the need to scratch their name into the top of the unit near the tape deck...

2nd Mar 2019, 5:11 pm	#1
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Bush Arena RA3700 schematic? Just wondering if anyone has, or knows of a source for, a service manual or schematic for a Bush Arena (Rank) RA3700 model stereogram? Have looked in the usual places and no mention of the system, only other reference to the model I could find was one for sale on that auction site but otherwise have drawn a blank. I've just picked one up from auction and, as well as the usual servicing of the Garrard SP25 MkIII turntable, it has very low output on the right channel & would appear to be a failing within the balance control circuit or perhaps the stereo/mono selector since output on the left channel remains high even when swinging the balance control. "buzz test" on the cartridge wires produces a loud response from both positive wires but only on the left channel, the right again is very low. This is with the selector in stereo or mono. (The balance pot on initial looks seems to be working, and indeed right channel output does increase marginally when swung all the way over, but without any significant cut in the left channel. Failing a schematic (it doesn't look that complicated of a circuit in all honesty) any suggestions as to what could cause this kind of thing would be much appreciated. Thanks, Dan.

2nd Mar 2019, 8:20 pm	#2
teetoon Heptode Join Date: Dec 2010 Location: Barnstaple, N.Devon, UK. Posts: 557	Re: Bush Arena RA3700 schematic? Hi Dan. The amplifier section is the A220 as in this recent post with a very useful schematic.https://www.vintage-radio.net/forum/...d.php?t=153781 Hope this helps. David.

2nd Mar 2019, 9:29 pm	#3
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Re: Bush Arena RA3700 schematic? Thank you for the link, the schematic seems to largely tally although the outputs are a different type but it's certainly similar enough to be a great help in tracing where things go/where they ought to go. Thanks very much.

3rd Mar 2019, 7:11 am	#4
Big jim Tetrode Join Date: Sep 2006 Location: South London, UK. Posts: 86	Re: Bush Arena RA3700 schematic? Sorry I don't have the circuit .but I'll put money on it being faulty 10mfd capacitors in the signal path the little gray ones

5th Mar 2019, 10:49 pm	#5
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Re: Bush Arena RA3700 schematic? The circuit is largely similar to the one linked in the thread above, I've made a start checking things while I had a few minutes earlier and the 250uF caps in the RIAA preamp were certainly iffy, I had a couple of usable pulls that have been fitted in their place, the 10uF on the RIAA seemed to check out but looking at the schematic and given your comment above I will likely have to buy a quantity of 10uF anyway so may replace them when I do the others. Next job is to start checking the caps on the main PCB. Thanks again for the links & suggestions.

23rd Mar 2019, 8:39 pm	#6
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Re: Bush Arena RA3700 schematic? Further to this thread (the RA3700 has been relegated to the rountuit pile for now), I now also have a model BS3049C (AudioSystem 1500) music centre. It's a lot different to the A220 circuit and has quite a few IC's on board. Still a fairly modular design but a lot "busier" inside & with a rough date from the latest IC of about 1978. I can find reference to only one other so far online, to do with the turntable and that ended not-so-well, with the whole thing drenched in WD40 I hardly need a schematic for the symptom I have (no output on one channel, just humming & the other channel working reasonably) but it'd be nice to have one handy in case I find other issues as well.

23rd Mar 2019, 9:12 pm	#7
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Re: Bush Arena RA3700 schematic? Indeed, one dead 220uF/25v cap on the amplifier board later and we have the Rock Show blasting out Feeder on both channels & in glorious stereo. I have to wonder who Al is though, and why he/she felt the need to scratch their name into the top of the unit near the tape deck...