Rectifier used in HMV 2022 Record Player.

[Murphyv310]

I can upload the diagram if needs be.

[Old Sparky]

Mark, as you know, since you kindly supplied it to me FOC, I do have quite a good Philips 'scope, which is here at home, whilst the record player is in my cellar workshop in town. I'll first try a known good ECL86, in the hope that cures the problem, before either taking the 'scope to the player or vice-versa. Meantime I will also check the o/p of the cartridge with a test record and my DMM, which should give a good enough indication at 1kHz. The staed o/p of a X5H is 1000mV, so I know what to expect, though I don't know offhand what the frequency response of my DMM is - I have the instruction booklet somewhere, though. The other points concerning the 2022's i/p circuitry I understand, and will bear them in mind.

[Mark Hennessy]

Oh, I hadn't forgotten - hence the smiley - but I didn't realise that it hadn't made it to your workshop yet.

Forgive the question, but how on earth do you cope with no 'scope in your workshop? I certainly couldn't. Previously I've recalled an engineer that I worked with many years ago - so apologies for the repetition if you remember the story - I would have been 16-17, and I'm guessing he was about 20 years older. A lovely guy who taught me loads, but one thing I struggled with was his attitude to the workshop 'scope (a nice 60MHz Hameg). For him, it really was an instrument of last resort, and he hardly ever used it - and certainly wasn't happy to let me loose with it! At home, I used mine all the time, and couldn't understand why you wouldn't. It was almost as if he was afraid to wear it out! Perhaps he wasn't confident using it? But either way, it really slowed down the fault-finding process. It's literally like working in the dark.

It was that experience that motivated me to sort you out with a working 'scope a couple of years back, so it's a bit of a shame that it's seemingly not being used. I can only hope that you're getting good use from it at home. Would you like another so you've got one at each locations? Later this year, once I've had a bit of time to sort things out, I'm planning to give away several of those 'scopes - otherwise they'll just end up being thrown in the WEEE skip. I'll be doing that via the forums when the time comes...

I'd want to check the specification of your DMM carefully before trusting it here. What model is it? In addition to frequency response, double-check the input resistance, as some are significantly lower compared to their DC resistance (which is usually 10M). Bear in mind that LF rumble will add to the signal (obvious on a 'scope, not so on a meter).

[Murphyv310]

Totally agree Mark.
A scope is like a third hand, something we all need and should use.
Testing the output on a DMM won't work with any accuracy, like Mark rightly says most have a low input impedance on AC. Time to marry the scope to the record player.

[ppppenguin]

Most old time radio and TV service guys didn't use a scope. If only for the simple reason that they were expensive. The more affordable scopes of those days had limited capability and weren't the easiest of things to use. Most faults could be found with an Avo and experience, without need for a scope. Component substitution was a common method of faultfinding. A signal generator and signal tracer helped to find trickier faults.

The time scopes became essential was for colour TV. It's more or less impossible to troubleshoot a decoder without a scope.

Like Mark and Trevor, the scope is almost part of me. It sits front and centre above the bench. Whether it's a simple 20MHz Hameg (Late 1960s TV service guys would have killed for something as good as this at an affordable price), my 400MHz Tektronix 2445B or a Rigol digital they all do a myriad of jobs with ease.

[Old Sparky]

I admit that I've used the Philips 'scope rarely, Mark, but i do repair things at home from time to time - I have 4 or 5 jobs on the go at the moment, mainly for people who live nearby, but the two main reasons I haven't taken it to the workshop are lack of space on the bench for it, plus the fact, that, as i don't drive, I'd have to carry it there, though there is a regular local bus from near where I live to town, so that's no excuse! There is actually a similar Philips 'scope in the 'waiting to do it' pile in the cellar - it belongs to someonr I've known for years, but I could meke use of it once it's repaired. I also have a small Russian 'scope, which is limited in it's facilities, but would no doubt help with this record player. Speaking of Hameg 'scopes, we used to have one in Malins workshop in Oxford, but that was sold when the firm closed down in 1995. As Jeffrey says, most faults can be located using a multimeter, signal generator and/or signal tracer, which is what I've been doing for the best part of 20 years now. My DMM is a M-3800, btw.

[Mark Hennessy]

This one? http://www.radiomuseum.org/r/metex_digit..._3800.html

Looks like this might be the manual for it: http://wrack.ped.muni.cz/datasheet/soubory/3800.pdf

In AC mode, it's a bit vague - it says <10M in parallel with >50pF. Frequency response is given as 40Hz to 1kHz, with no limits given. The latter is easy to check with some form of signal generator, but I do wonder about the capacitance. Especially as ">50pF" could mean 1uF if we took it literally (though obviously I'm just being silly there ). Perhaps it's worth checking with a known-good cartridge of similar type, if that's feasible to arrange? But here's where the 'scope wins, as it'll be 1M in parallel with 20pF (plus the cable capacitance), or 10M in parallel with single-digit values of pF, depending on your x10 probe.

I can certainly appreciate that lugging a 'scope to your workshop could be difficult. And depending on how dry the cellar workshop is, perhaps it might be best to leave it at home?

When working on older gear, I have found that the balance between 'scope and DMMs has shifted slightly towards the DMM. That's partly because of the simpler nature of the circuitry, and partly because I've bought some nice DMMs in recent times, having only had a CPC cheap one for about a decade (and was horrified to see how inaccurate it was when I finally treated myself to a posh Fluke). Not that accuracy is a bit deal for radio repairs, but sometimes it's needed.

But having said that, the times when I've given myself the run-around were when I didn't use the 'scope!

[Old Sparky]

I've just looked up the RadioMuseum page, and that Manual, Mark, and was also concerned about that spec. being quoted as <10M in parallel with >50pf. As you say a bit vague. I do have the printed operation Manual somewhere, but it no doubt states the same as the on-line one! My M3800 is the Chinese made one, not the S. Korean Metex original. I still have a Fluke 75, but the rotary switch, or more correctly, the 'click stop' facility in that failed. As to the cellar, yes it does get damp, and, because of that, I've had to repair my AM/FM signal generator twice, when it had never given any trouble before. I'll try another valve in the R/Player, and check the cartridge's o/p with the M3800, then, if neccesary, take it from there. (and this was going to be a nice simple job!!!)

[Mark Hennessy]

What's wrong with the Fluke - is it the plastic detent "spring"? I might be able to help with that - after sorting out our "fleet" a few years back, I was left with various random bits of case, etc, and might well have the part you need.

[Old Sparky]

It was to do with that, Mark, but also the range switch itself. About 2 or 3 years ago a member of UKVRRRDF kindly sent me a similar model Fluke with a cracked display, from which I removed the range switch and carefully fitted to my Fluke, but it still had faultsso it's been put to one side.