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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 23rd May 2020, 10:08 pm   #21
MotorBikeLes
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Default Re: Oscilloscope question - not vintage

WME Bill mentioned a good few scopes earlier, with which i would mostly agree.
I will offer just two, a valved scope and an all solid state one, bearing in mind the OPs needs. A Telequipment S32. Simple valve job, up to 10MHz bandwidth, everything replaceable or repairable. Very old, but stonking little 'scopes.
For the solid state, go with any of the D65, D66, D67 or D67A. 15 to 25MHz bandwidth, single or dual timebase, simple to operate and everything is off the shelf stuff. No magic ICs or other strange stuff.
Perhaps I should have thrown in the S54A as a basic solid state 10MHz scope as well.
If any of these has a good CRT (and quite a few replacements available if not) and a GOOD MAINS TRANSFORMER, you are good to go. Only Mains transformers could be difficult to obtain, everything else that is critical is easily found.
Les.
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Old 25th May 2020, 12:48 pm   #22
hillmanie
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Default Re: Oscilloscope question - not vintage

Quote:
Originally Posted by Radio Wrangler View Post
Quote:
Originally Posted by hillmanie View Post
Insofar as I can think ahead I only need it to measure and examine the waveform of AF voltages in intervalve amplifier circuits looking for distortion TT
Ah, you may be heading for a small pitfall.

You're planning your scope needs around the signals you expect to have in a working piece of gear.

You will also come across things which go unstable and oscillate. A low bandwidth scope might not show this and give you a smooth low freq trace that looks OK.

I'd suggest you should get at least a 10 or 20MHz scope to cover the sorts of misbehaviours you'll come across. Any less and you'll miss some clues that could make life a lot easier.

Two channels are handy for comparing things. You'll get along fine without needing more.
David
Timely warning thanks. I may learn something from working on two of the exact same model which - Murphy's Law permitting may have different fault symptoms. I may be able to compare a working piece of circuit from one recorder with the same section of the faulty one. (I expect to always have a working clone as I, Heaven forgive me have been buying 10 junkers to a number of thirty five currently. Since a lot of British manufactures seem to use the same circuitry I'm hoping to gain experience that way
Tony
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Old 25th May 2020, 1:44 pm   #23
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Default Re: Oscilloscope question - not vintage

An example of what David (Radio Wrangler) speaks !

here

dc
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Old 27th May 2020, 6:47 pm   #24
Chris55000
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Default Re: Oscilloscope question - not vintage

Hi!

Scopex and Gould oscilloscopes regularly crop up fairly regularly, but both are beset with problems – Scopex have tunnel diode triggering, and there are also mains transformer problems, and Gould bookwork is horrible to read due to there being no component–values or working voltages given on their diagrams, and spares problems need another parts mule!

You can get new Chinese 10MHz CRT scopes but I have found they have very short–lived CRTs and their print is horrible to work on – it curls up and dies if you wave an iron anywhere near it!

I posted a detailed A–Z review in the thread "Two Scopes – Which One Is Best" covering most of the ones found regularly on the secondhand market.

Chris Williams
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Old 27th May 2020, 8:23 pm   #25
MotorBikeLes
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Default Re: Oscilloscope question - not vintage

Chris, not sure if you are correct. I don't recall ever seeing a tunnel diode in a Scopex.
The two common models are the 4D10 and the 4D10A. The first one used static sensitive components in the front end (BFS28 MOS-Fets), so need treating with care. The -A version used less sensitive devices, ordinary FETs, E421. (Not sure what equivalents, but possibly selected BFW10 or BFW11).
Common failures are the high value resistors in parallel with the high voltage electrolytics in the EHT chain.
My complaint about gould (aka Advace) is transformer failures.
10MHz conventional Chinese scope, never hear of them. Details please?
Les.
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Old 27th May 2020, 10:28 pm   #26
factory
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Default Re: Oscilloscope question - not vintage

I had a quick search & found some Chinese sites selling analogue CRT scopes, the cheapest is a 2MHz model (with round CRT) at around $60-70 and some 20MHz & higher models for more $, no idea what the quality is like as I've never used any of these, or bought from that site.

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David
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Old 28th May 2020, 5:07 pm   #27
Chris55000
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Default Re: Oscilloscope question - not vintage

Hi!

Rest assured the 4D25 has a 1N3719 (D307) t.d. hidden away very carefully in the trigger input circuit diagram – it's used to discharge a current pulse into the primary of the trigger pulse coupling transformer T501!

Chris Williams
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Old 28th May 2020, 7:56 pm   #28
MotorBikeLes
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Chris, I have never met a 4D25. Don't expect i ever will now, but if one does come my way ---.
For the record, i have a small stash of new TDs, mostly 4.7mA if I recall. All genuine, bought in a lot at auction some 30 to 40 years ago. I have had or worked on quite a few scopes over the years, but there must be many tens of them that I have never met for every one I have.
Les.
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Old 28th May 2020, 11:41 pm   #29
Chris55000
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Default Re: Oscilloscope question - not vintage

Hi!

I have one disguised as the Farnell 4D–30 in my collection and a recently acquired Cossor 3100/CDU160 with four (!!) of the dreaded t.d.'s in it so I fear a little portion of next month's salary is going to go on some 1G304s, as the Cossor refuses to trigger properly on the simplest waveform, but I'll wait for the bookwork on the way from Bill Nichols first!

Chris Williams
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Old 29th May 2020, 8:05 pm   #30
MotorBikeLes
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Default Re: Oscilloscope question - not vintage

Chris, I remember Peter Waugh telling me that the Farnel branded versions of the 4D10 series were sold as 4D12. This was achieved by smaller divisions on the screen, so the bandwidth Xs Gain relationship remained intact. That would probably mean the 4D30 by Farnell has smaller divisions than a Scopex 4D25.
What rating are the TDs you require? My books do not list a 1G304.
Les.
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Old 30th May 2020, 9:24 am   #31
Chris55000
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Default Re: Oscilloscope question - not vintage

Morning Les!

It's the Russian "GI304B" 4.7mA AEY25 equivalent type – just me making the usual typos with Russian type designations again!

Chris Williams
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Old 30th May 2020, 9:56 pm   #32
MotorBikeLes
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Chris, just found some notes that tell me I have some 1N3716 TDs, 4.7mA same as the AEY25. I MAY even have some AEY25s as well. I am still reorganising stuff after redecorating the "electronics room", so not too sure where they are right now.
Les.
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