Feedback TWG Function Generator - UK Vintage Radio Repair and Restoration Discussion Forum

Diabolical Artificer · 15th Aug 2015, 12:31 pm

Has anyone a schematic or manual for the above? The one I have has no OP.
I've reformed the two big reservoir caps and had a signal out of the 2v sine/square/triangle OP's (2v 1000 ohm ), however when I turned the voltage output pot fully clockwise, the trace got cut off at the bottom. I found a loose wire on the bridge rectifier, which was probably the cause. There was nothing from the red/black terminals on the right.

However, I now have nothing except a floating DC trace on the scope. By floating I mean the trace floats up and down on the screen. I've checked the power rails and have +/- 19v. All a visual check has thrown up is a few possible
dry joints and a scorched resistor near the output.

Any help most welcome,

Andy.

karesz* · 15th Aug 2015, 3:52 pm

Hi Andy,
I think you dont have GND connection between bridge and circuit-find a right "place" for the loose wire. Your floating trace on scope must be hum of mains...
Karl

Freya · 15th Aug 2015, 7:27 pm

It may help to to email Feedback at Crowborough, I did this for my PFG605 last year and got the full service manual emailed back to me, very helpful.

Diabolical Artificer · 16th Aug 2015, 5:41 am

Thank's Stephen, didn't realise FB were still in business, I'll drop them an email.

Andy.

15th Aug 2015, 12:31 pm	#1
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Feedback TWG Function Generator Has anyone a schematic or manual for the above? The one I have has no OP. I've reformed the two big reservoir caps and had a signal out of the 2v sine/square/triangle OP's (2v 1000 ohm ), however when I turned the voltage output pot fully clockwise, the trace got cut off at the bottom. I found a loose wire on the bridge rectifier, which was probably the cause. There was nothing from the red/black terminals on the right. However, I now have nothing except a floating DC trace on the scope. By floating I mean the trace floats up and down on the screen. I've checked the power rails and have +/- 19v. All a visual check has thrown up is a few possible dry joints and a scorched resistor near the output. Any help most welcome, Andy. Attached Thumbnails __________________ Curiosity hasn't killed this cat...so far.

15th Aug 2015, 3:52 pm	#2
karesz* Heptode Join Date: Jun 2010 Location: Zurich, Switzerland Posts: 538	Re: Feedback TWG Function Generator Hi Andy, I think you dont have GND connection between bridge and circuit-find a right "place" for the loose wire. Your floating trace on scope must be hum of mains... Karl

15th Aug 2015, 7:27 pm	#3
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,990	Re: Feedback TWG Function Generator It may help to to email Feedback at Crowborough, I did this for my PFG605 last year and got the full service manual emailed back to me, very helpful. __________________ Stephen _________"It`s only an old telly" ___

16th Aug 2015, 5:41 am	#4
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Re: Feedback TWG Function Generator Thank's Stephen, didn't realise FB were still in business, I'll drop them an email. Andy. __________________ Curiosity hasn't killed this cat...so far.