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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.

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Old 14th Jan 2020, 2:09 pm   #1
Uncle Bulgaria
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Default Audio Signal Generator & Bench PSU

Ahoy,

I'm on the lookout for an audio signal generator suitable for probing problems in valve and transistor circuits, then aligning them when done. I haven't got into the radio frequency side of things so that's not a requirement. I don't need bells and whistles and complexity, both from being a rank amateur and from being impecunious. Has anyone got one gathering dust?

I've seen some of the marvellous DIY ones on here, but have managed to resist the urge to build a chain of projects to get to fixing the one I started with...

I'd like a PSU to stop me having to make various hook-ups from other pieces of equipment, or have mains floating about while I'm looking at other parts of the circuit. The circuit I'm looking at now has lines up to 44V, so I expect 60V would be more useful than 30. Is a dual supply worthwhile?

I'm considering visiting either Audiojumble or my first foray to a BVWS at Harpenden...perhaps these things are best found at one of those?
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Old 14th Jan 2020, 2:16 pm   #2
HamishBoxer
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Default Re: Audio Signal Generator & Bench PSU

Yes indeed ,they do turn up at Harpenden and I would say go if you can.
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Old 14th Jan 2020, 2:26 pm   #3
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Default Re: Audio Signal Generator & Bench PSU

Audiojumble and BVWS are possibilities, but you might have better luck at an amateur radio rally, there are often stalls selling second-hand test equipment. I've bought quite a lot of test gear from such events. An element of luck is involved.

Dual power supplies are OK, but you can use multiple supplies at once. Think also of how much current you'll need. Getting one with an adjustable current limit control is a big plus.

Cheapie Chinese power supplies 30v at a few amps are under a hundred quid new and the ones ar work seem to work just fine. Use this as a benchmark for haggling!

Audio generators come in two flavours. Wien-bridge oscillators are low distortion and usually give you sine or square outputs. 'Function generators are more versatile with a menu of different wave shapes, but the distortion on sines is not so good.

David
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Old 14th Jan 2020, 3:00 pm   #4
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Default Re: Audio Signal Generator & Bench PSU

If you're into tape and general audio a Ferrograph test set is a handy tool when up to spec, eg: Ferrograph RTS2.....Low distortion audio gen, wow and flutter meter, distortion meter, AC voltmeter (wide response) etc etc.

https://www.historyofrecording.com/Ferrograph_RTS2.html

Manual here:

https://www.warwickelectronics.com/i...ers_manual.pdf

Had a Ferrograph test set when I worked for Sony, wouldn't have been without it that's for sure.

Lawrence.
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Old 14th Jan 2020, 3:41 pm   #5
Electronpusher0
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Default Re: Audio Signal Generator & Bench PSU

I have a Lyons SQ10 spare if thats any good. See photos.
Works OK, the output level pot has been replaced with a 10 turn precision pot with counter.
Being Wein bridge stabilised by thermistor the amplitude does "bounce" a little when first setting frequency but radidly stabilises.
10 plus postage if you want it.

PM me if interested.
Peter
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Old 14th Jan 2020, 5:16 pm   #6
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Default Re: Audio Signal Generator & Bench PSU

A radio frequency generator is a must from what you say in your first post - far more than just an audio frequency generator.

An Advance E2 is the most common and has a fixed audio frequency output as well as all the RF frequencies.

There was someone selling one on here a while ago and I don't think it ever sold, probably because it was a collection only job and the price was a little high at 25 for its condition and for what it was, but maybe worth following up if you can locate the old thread on it.
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Old 15th Jan 2020, 1:22 pm   #7
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Default Re: Audio Signal Generator & Bench PSU

Strange - I replied to this yesterday!

I've got in touch with ElectronPusher0 as that Lyons seems to be the business.

Techman - I'm intending to test audio circuits and calibrate them with signals specified in the manuals, so what do I need the RF parts for? The Advance E2 looks like the real deal, though!

Radio Wrangler - I have had a check in the paper and online for radio rallies, but I don't think Cornwall supports the density of population. For the PSU, I was thinking a highish current for testing valve heater chains, and a current limiter on the higher voltage for fault conditions in transistors. I don't think it's worth seeking a high voltage supply when the valve equipment's PSU should be able to do that itself. As I don't need all the functions of a function generator, I think the low distortion is for me!

Lawrence - I've had my eye out for an RTS2 for a while. I'd love one! They seem to be just what I need for my interests. However, there was one on eBay for a while for 800, and while one did sell at the BVWS for something much more affordable, it was a couple of years ago so they're not common. But yes, ideal...
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Old 15th Jan 2020, 1:36 pm   #8
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Default Re: Audio Signal Generator & Bench PSU

Quote:
Originally Posted by Techman View Post
A radio frequency generator is a must from what you say in your first post - far more than just an audio frequency generator.

An Advance E2 is the most common and has a fixed audio frequency output as well as all the RF frequencies.

There was someone selling one on here a while ago and I don't think it ever sold, probably because it was a collection only job and the price was a little high at 25 for its condition and for what it was, but maybe worth following up if you can locate the old thread on it.
That was mine. Its sold now, in the end I listed on ebay and within 5 hours had a commitment to buy it for 35 and collect it the next day.
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Old 15th Jan 2020, 2:49 pm   #9
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Default Re: Audio Signal Generator & Bench PSU

RTST2 ;
http://www.stewart-of-reading.co.uk/
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Old 15th Jan 2020, 3:09 pm   #10
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Default Re: Audio Signal Generator & Bench PSU

If it is still there, grab it, it's a bargain. Otherwise, I still have a Ferrograph RTS2 and ATU for sale at 250 the pair if you don't find anything else

Intended as a tape recorder test set the RTS2 incorporates an audio oscillator and distortion meter as well as wow and flutter, audio millivolt meter etc and I have two 3KHz test cassettes for wow and flutter.

I have owned them from new and they have had very little use. They are in excellent condition. Until 12 months ago they were stored in a heated workshop, now they are in the loft.

Last edited by See_Mos; 15th Jan 2020 at 3:16 pm.
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Old 15th Jan 2020, 11:57 pm   #11
Uncle Bulgaria
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Default Re: Audio Signal Generator & Bench PSU

Great find, Restoration73 - I have sent them an e-mail. Fingers crossed!

Thank you too, See_Mos for the generous offer. Alas, 250 is too much for me to justify, though they look marvellous pieces of kit - I imagine myself as being at the stage of most people on this forum in the '60s & '70s - bodging things up for cheapness! If I can get the Stewart's RTS2 at 50 I'll be very happy.
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Old 16th Jan 2020, 3:30 pm   #12
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Default Re: Audio Signal Generator & Bench PSU

Alas, the Stewart's one has gone...
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Old 16th Jan 2020, 4:48 pm   #13
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Default Re: Audio Signal Generator & Bench PSU

Quote:
Originally Posted by Uncle Bulgaria View Post
signal generator suitable for probing problems in valve and transistor circuits, then aligning them when done.
I know you said 'audio' in your first post, but the statement you made above regarding 'aligning' really refers to RF and IF circuits in radios. Forgive me if I'm wrong, but your statement above tells me that you don't really know exactly what you do want.

I've got a nice Advance audio signal generator with all the audio frequencies on it and to be truthful, I used it just once last year and that was only because it happened to be easier to grab and take into another room as it didn't have things connected up to it, which was the case with the E2 which would have been just as good for the purpose with its single fixed audio frequency.

If you're going to be working on radios, then you'll need RF frequencies. If you're just going to be working on audio gear, the go for an audio generator only, but if you're thinking that you'll need all those audio frequencies for what you intend to do, then you're going to need a lot more kit than just that generator.

I regard a bespoke audio frequency generator the same as a valve tester, as 'nice to have' item to play around with, but completely unnecessary most of the time.

If you've got the chance of an AF generator at the right price, then go for it!
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Old 26th Feb 2020, 2:06 am   #14
Uncle Bulgaria
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Default Re: Audio Signal Generator & Bench PSU

I used the term loosely, I must admit! I wasn't aware that it had a specific radio meaning. I haven't any training in the dark electronic arts, so you're quite right I don't know exactly what I do want.

I do know that I have some awkwardness getting a 1kHz sine wave from my PC or 'phone with any kind of reproducibility, and don't particularly want them hooked up to equipment under test.

I have a couple of transistor amplifiers and the Ferrograph to look at currently, and am going to use the generator and millivoltmeter kindly supplied by Electronpusher0 to chase down the signals.

I got a PSU at Audiojumble somewhat at random as it was the only one I saw, it was very cheap and it looked decent and solid - a Farnell SB30/10. My back certainly felt its solidity after carrying it across London for two days. Good for a lot of things, but not for limiting to low currents! I think I'm still on the lookout for a less beefy unit, or I learn to make an adjustable current limiter (or perhaps a bulb in series...) It's done a nice job on my MGB batteries, though!
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Old 26th Feb 2020, 8:15 am   #15
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Default Re: Audio Signal Generator & Bench PSU

In the audio world, tasks like setting levels and setting up Dolby noise reducers is sometimes called alignment. So the word without context is ambiguous and it's easy for two people to see it and assume their own usual context.

In the RF world, adjusting the tuning of a radio to match its scale, to adjust RF tuned circuits to track the tuning, and adjusting IF tuned circuits to the intended bandpass shape and centre frequency are all called alignment.

David
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Old 26th Feb 2020, 1:14 pm   #16
Uncle Bulgaria
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Default Re: Audio Signal Generator & Bench PSU

Thank you, David. I'm glad we're now all aligned on this. I suppose it's a problem to be aware of on a forum populated by dilettantes and professionals of many years' standing.
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Old 26th Feb 2020, 2:41 pm   #17
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Default Re: Audio Signal Generator & Bench PSU

This is a restful place compared to many.

I remember the early years of the amateur radio newsgroups and their perpetual flamewars. I don't know if they're still raging - I haven't been back for a long time. The audio field with only a few exceptions does not seem a friendly place either. The horsey part of the internet seems very friendly. Is it something about electronics, I wonder?

David
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