NAD 7130 Tuner fault help - UK Vintage Radio Repair and Restoration Discussion Forum

rjmusto · 11th Feb 2024, 6:11 pm

Hi all,
I am a bit off-pieste (usually on Ham radio or test equipment repair, not hifi), trying to fix a NAD 7130 Tuner Amp and am needing a bit of help to work out where to go with this.

The audio amp side is working fine, but the tuner side is sort of working but not quite right... I can auto and manually tune to a station, but the audio is muted, except whilst manually tuning. So you can tune in to a station but not listen to it.

So far I have found that the MUTE signal from IC6 pin 12 is switching up and down as you tune past a station and this is appearing on Pin 12 of the synthesiser. But the Mute control output on Pin 36 does not change, so the audio remains muted. I have not managed to find a datasheet for the TC9137 synth, so not sure if there is some other input to it that is inhibiting the audio.

Any suggestions for what to look for would be much appreciated.

I should add that I have re-capped the whole board, having found the majority of electrolytics to be bad.

Thanks,
Ralph

rjmusto · 23rd Mar 2024, 8:20 pm

Looks like not many folk here work on NAD audio stuff....

The problem I discussed here was due to a faulty synthesiser chip - the Mute output is stuck high.

Trying to source a replacement is proving tricky, prices for the chip and/or postage (to Ireland) I've seen on eBay seem a little bonkers.

I dont suppose anybody here has one I could purchase?
It's a :
TC9137AP

Thanks,
Ralph

djsbriscoe · 23rd Mar 2024, 8:52 pm

Littlediode are accepting offers on eBay. I've had offers accepted when buying parts off them. Postage should be cheap enough from London to Ireland. Seems the only other choice is bulk buying a few thousand from a wholesaler.

Marconi_MPT4 · 24th Mar 2024, 7:27 pm

Quote:

Originally Posted by rjmusto

I have not managed to find a datasheet for the TC9137 synth

I am not sure if you have seen this data sheet? https://datasheetspdf.com/pdf-file/5...iba/TC9137BP/1

Page 150 paragraph 6 Muting Output describes the various modes which may affect the output.

Rich

rjmusto · 29th Mar 2024, 9:04 pm

Thanks for the replies - have been laid low by a nasty bug, so sorry for the delay in replying.

I hadn't seen such a detailed spec sheet up to now. So very useful, thanks.

And the LittleDiode option noted.

Ralph

Radio Wrangler · 29th Mar 2024, 9:51 pm

That is a good, thorough data sheet, and what looks like a quite useful part for its era. Of course, there is one small howler in the data sheet. It's unlikely that a native English speaker would choose the name "Pee Sound" for something.

David

11th Feb 2024, 6:11 pm	#1
rjmusto Pentode Join Date: Feb 2012 Location: Mountain Castle, Modeligo, County Waterford, Republic of Ireland. Posts: 193	NAD 7130 Tuner fault help Hi all, I am a bit off-pieste (usually on Ham radio or test equipment repair, not hifi), trying to fix a NAD 7130 Tuner Amp and am needing a bit of help to work out where to go with this. The audio amp side is working fine, but the tuner side is sort of working but not quite right... I can auto and manually tune to a station, but the audio is muted, except whilst manually tuning. So you can tune in to a station but not listen to it. So far I have found that the MUTE signal from IC6 pin 12 is switching up and down as you tune past a station and this is appearing on Pin 12 of the synthesiser. But the Mute control output on Pin 36 does not change, so the audio remains muted. I have not managed to find a datasheet for the TC9137 synth, so not sure if there is some other input to it that is inhibiting the audio. Any suggestions for what to look for would be much appreciated. I should add that I have re-capped the whole board, having found the majority of electrolytics to be bad. Thanks, Ralph

23rd Mar 2024, 8:20 pm	#2
rjmusto Pentode Join Date: Feb 2012 Location: Mountain Castle, Modeligo, County Waterford, Republic of Ireland. Posts: 193	Re: NAD 7130 Tuner fault help Looks like not many folk here work on NAD audio stuff.... The problem I discussed here was due to a faulty synthesiser chip - the Mute output is stuck high. Trying to source a replacement is proving tricky, prices for the chip and/or postage (to Ireland) I've seen on eBay seem a little bonkers. I dont suppose anybody here has one I could purchase? It's a : TC9137AP Thanks, Ralph

23rd Mar 2024, 8:52 pm	#3
djsbriscoe Pentode Join Date: May 2015 Location: Hemel Hempstead, Hertfordshire, UK. Posts: 133	Re: NAD 7130 Tuner fault help Littlediode are accepting offers on eBay. I've had offers accepted when buying parts off them. Postage should be cheap enough from London to Ireland. Seems the only other choice is bulk buying a few thousand from a wholesaler.

29th Mar 2024, 9:04 pm	#5
rjmusto Pentode Join Date: Feb 2012 Location: Mountain Castle, Modeligo, County Waterford, Republic of Ireland. Posts: 193	Re: NAD 7130 Tuner fault help Thanks for the replies - have been laid low by a nasty bug, so sorry for the delay in replying. I hadn't seen such a detailed spec sheet up to now. So very useful, thanks. And the LittleDiode option noted. Ralph

29th Mar 2024, 9:51 pm	#6
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,917	Re: NAD 7130 Tuner fault help That is a good, thorough data sheet, and what looks like a quite useful part for its era. Of course, there is one small howler in the data sheet. It's unlikely that a native English speaker would choose the name "Pee Sound" for something. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done