UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Offered and Wanted Messages > Sets, Parts and Service Information Wanted (private buyers only, no swaps)

Notices

Sets, Parts and Service Information Wanted (private buyers only, no swaps) If you need help obtaining components, sets or equipment, post a message here. Private buyers only - no traders. No swaps.

Reply
 
Thread Tools
Old 18th Jun 2020, 9:44 am   #1
Cakebread
Diode
 
Join Date: Jun 2020
Location: London, UK.
Posts: 9
Default Feedback models VPO230 & TWG300 - manual needed

Hello everyone,

This is my first post in this forum, so I hope I've got things right...

Following a lab clearance, I've acquired two Feedback instruments, a VPO230 variable phase oscillator and a TWG300 sine/square/triangle wave generator. I know that both were functional 20 years ago and have been stored since.

Before I even think about checking capacitors & so forth, it would be very useful indeed to have circuit diagrams or - ideally - manuals. The people at Feedback have been helpful, but tell me that their archives do not go this far back; fair enough, these must be 50+ years old.

So, can anyone here help me? I'd be happy to reimburse postage & copying costs of course.

Thanks, Andy
Cakebread is offline   Reply With Quote
Old 19th Jun 2020, 2:07 pm   #2
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 5,361
Default Re: Feedback models VPO230 & TWG300 - manual needed

When I got a Feedback function gen I emailed FB; they sent me three scan's of microphiches, shame they couldn't help in your case.

You could Phil, i think it is at Telford, see here - http://www.telford-electronics.co.uk/manual.php?alpha=f your models aren't listed but he may have something. That or a TWG500 manual might be similar to the 300 to give you something to go on.

Andy.

PS, I see there's a TWG501 manual on ebay.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline   Reply With Quote
Old 19th Jun 2020, 4:12 pm   #3
Cakebread
Diode
 
Join Date: Jun 2020
Location: London, UK.
Posts: 9
Default Re: Feedback models VPO230 & TWG300 - manual needed

Thanks Andy, much appreciated.

Can't fault the people at Feedback for trying. They sent me a TWG500 manual on the off chance it would help, looks like the 500 has variable phase as well as the various waveforms. The big difference of course is the 500 has transistors & the 300 has valves.

I'll try Phil at Telford and see how things go.

Best, Andy
Cakebread is offline   Reply With Quote
Old 20th Jun 2020, 7:06 am   #4
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 5,361
Default Re: Feedback models VPO230 & TWG300 - manual needed

"the 300 has valves." Does it? Wow, I thought all FB stuff was SS, any chance of some pics please? If it's valved with hardwired connections back engineering should be easier.

I love FB stuff, small, neat, well made modules with lots of functionality, unfortunately it's beyond my ken how it works. A few years ago there was about 100 different units on Ebay that looked like most was for schools/colleges. There were various modules like oscillators, attenuators, amps, PSU's etc all with the FB block diagram type legend on the front that plugged into each other via 4mm banana jacks.

Good luck, Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline   Reply With Quote
Old 20th Jun 2020, 4:59 pm   #5
Cakebread
Diode
 
Join Date: Jun 2020
Location: London, UK.
Posts: 9
Default Re: Feedback models VPO230 & TWG300 - manual needed

Yes, both the VPO230 & TWG300 are valve units. At a guess, the TWG300 is a predecessor of the TWG501, it seems to have similar ranges & choice of outputs - a good bit chunkier though of course.

Quite agree about the build quality and general 'feel', that's one of the reasons I'd like to have these 2 sorted & working. Most of the innards are on PCB's which complicates back engineering a bit.

I'll do some photo's as soon as I can resurrect/replace my cheapo camera.

Best, Andy
Cakebread is offline   Reply With Quote
Old 22nd Jun 2020, 9:35 am   #6
Cakebread
Diode
 
Join Date: Jun 2020
Location: London, UK.
Posts: 9
Default Re: Feedback models VPO230 & TWG300 - manual needed

Well, I emailed Telford Electronics & Marc had nothing on the VPO230 and the nearest he had to the TWG300 was a TWG500. Nice quick, friendly answer though.

I think I'll have to put these two aside for a while as things are a bit hectic at work with the building coming back to life. The camera has definitely died so a little point & shoot thing is on order and pictures will be sent.

Just pulled the covers off the 300 - only 4 electrolytics to worry about, all 32uF/450V. One might have leaked, seems easy enough to replace all 4. Looks like there are 2 HT supplies on the one board, both with 2x BY100 rectifiers plus 4x ECL82's & an 85A2. Then 2 other pcb's and a lot of ECC8x valves. Takes me straight back to schooldays & first holiday job!

This is a lower frequency generator than I thought, range is 0.001 - 1000 cycles/second with a secondary scale in seconds/cycle, never seen that before.

Thanks for your help - and if there's anyone else out there...

Andy
Cakebread is offline   Reply With Quote
Old 28th Jun 2020, 10:51 am   #7
Cakebread
Diode
 
Join Date: Jun 2020
Location: London, UK.
Posts: 9
Default Re: Feedback models VPO230 & TWG300 - manual needed

Sorry for the delay, here are some pictures of the TWG300, I hope they're useful. Will post some of the VPO230 as soon as these arrive safely.

Best, Andy
Attached Thumbnails
Click image for larger version

Name:	TWG300 Front Panel.jpg
Views:	31
Size:	88.4 KB
ID:	209672   Click image for larger version

Name:	TWG300 Left Side 1.jpg
Views:	30
Size:	117.6 KB
ID:	209673   Click image for larger version

Name:	TWG300 Left Side 2.jpg
Views:	28
Size:	107.0 KB
ID:	209674  
Cakebread is offline   Reply With Quote
Old 28th Jun 2020, 2:04 pm   #8
Cakebread
Diode
 
Join Date: Jun 2020
Location: London, UK.
Posts: 9
Default Re: Feedback models VPO230 & TWG300 - manual needed

And here are some pictures of the VPO230, hope they're useful. Andy, if you'd like different angles or whatever, I'll see what I can do.

Best, Andy
Attached Thumbnails
Click image for larger version

Name:	VPO230 Front Panel.jpg
Views:	18
Size:	80.5 KB
ID:	209705   Click image for larger version

Name:	VPO230 Left Side.jpg
Views:	21
Size:	128.9 KB
ID:	209706   Click image for larger version

Name:	VPO230 Right Side.jpg
Views:	23
Size:	61.2 KB
ID:	209707  
Cakebread is offline   Reply With Quote
Old 29th Jun 2020, 7:06 am   #9
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 5,361
Default Re: Feedback models VPO230 & TWG300 - manual needed

Thanks Andy, those two look really nice & well built. A lot of the components and layout used in their later gear are present here, big solid case, Welwyn prescision resistors, big polystyrene caps on a separate board, Colvin pots, wow, look at the size of that in the TWG300 ( would hate to have to find a replacement for it) looks like the same person or people designed the later stuff. The boards and cast case frames look similar to Telequipment gear.

Both should be relatively easy to trace the circuit, the TWG300 has what looks like a regulated PSU on the LHS, looks like a voltage reference valve there, the middle board is the oscillator, with what looks like the range R's & C's at the bottom. There might be an output transformer or similar underneath that board. The VPO230 looks a little later, solid state rectification, I'd love to see the circuit for the phase control, that looks like the second smaller board.

BTW have you powered them up yet and checked if you have an OP? If you bring them up slow they should be ok,there doesn't look to be any physical damage I can see, apart from the usual scorching around resistors on the PCB, be careful with the boards if you do any soldering, the traces lift easily and are easily damaged.

Thanks again for the pics, hope you get them working, but if you ever to decide to sell them on, let me know. Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline   Reply With Quote
Old 30th Jun 2020, 4:22 pm   #10
Cakebread
Diode
 
Join Date: Jun 2020
Location: London, UK.
Posts: 9
Default Re: Feedback models VPO230 & TWG300 - manual needed

A pleasure Andy. As you say, well thought out & solidly built; the designer was given a fairly free hand & enjoyed himself I think. Hadn't thought of it, but now you mention Telequipment I see what you mean.

I think you're right, regulated psu - x2 on the same board I think - at the back of the 300, then the oscillator & o/p circuitry further forwards. I've just realised I only sent photos of the left side, here are 2 of the right hand.

I haven't run these up yet, in the middle of clearing space and plucking up courage! As I said in my original post, I know they both worked 20 years ago (when they were presumably 35-odd years old) & have been stored well since, so they might well work straight off. Perhaps run power through a variac to start with? There's a trace of what could be a leak on one of the psu electrolytics (TWG300); if I change 1 I'll do all 4.

Thanks for the reminder about delicate boards, been caught that way before. Quite a while since I did anything serious with valve gear, but these 2 are going to be a good way of playing myself back in. Might have to wait a while until work calms down a bit. I will remember you if I decide to sell, but suggest you don't hold your breath!

All the best, Andy
Attached Thumbnails
Click image for larger version

Name:	TWG300 Right Side 1.jpg
Views:	11
Size:	128.0 KB
ID:	209918   Click image for larger version

Name:	TWG300 Right Side 2.jpg
Views:	9
Size:	103.5 KB
ID:	209919  
Cakebread is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 10:32 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.