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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 3rd Jan 2022, 9:51 pm   #41
Gulliver
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

Ye gods....I owned one of these in the 1980s, bought from a charity shop. What amazed me was that it was significantly worse in all respects than the early 60s and late 50s mono reel to reel machines I had at the time. Upon opening it up I discovered it was transistorised rather than the expected valves - which I should have expected after realising that it didn't need to "warm up".

Sound quality was *dire*. I can well believe that scathing review which found frequency response was 300-4kHz. And the plastic casing rattled or resonated at several frequencies.

What one could say for it, was that it was reliable. But even the Fidelity Argyll Minor was better sounding, and that was another basic model.

But....it seems unusual. It seems scarce these days. So might be worth saving as an interesting item. None of those 60s mono machines was great shakes in the audio stakes anyway. This one is at least somewhat different to most. Sadly mine is long gone.
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Old 7th Jan 2022, 12:12 am   #42
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

Hi!

Member "Slidertogrid" Rich has now sent a Transistorised Fidelity Playmaster board (4–TR version) to me, from which I will be beginning some circuit and PCB layout diagrams over the next week or two!

I may possibly need some underneath photos from the OP's machine to clarify such matters as wiring/wiring colours, etc., but I'll request these as I come to those parts of the circuit!

Chris Williams
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Old 7th Jan 2022, 12:45 am   #43
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

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Originally Posted by Chris55000 View Post
Hi!

Member "Slidertogrid" Rich has now sent a Transistorised Fidelity Playmaster board (4–TR version) to me, from which I will be beginning some circuit and PCB layout diagrams over the next week or two!

I may possibly need some underneath photos from the OP's machine to clarify such matters as wiring/wiring colours, etc., but I'll request these as I come to those parts of the circuit!

Chris Williams
Hi Chris,

Let me know what you need, it will be in pieces for a while. I am making a bit of progress, so should be able to post an update soon.

Tony.
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Old 7th Jan 2022, 10:26 am   #44
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

It would be extremely helpful if it could be ascertained from its circuit just why the Transistorised Playmaster had such a dreadful frequency response and measures so badly.
Ever since its review in 1966, I’ve wondered how Fidelity could have made such an awful tape recorder, and actually submitted it for a technical review!
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Old 7th Jan 2022, 12:11 pm   #45
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Originally Posted by david freeman View Post
It would be extremely helpful if it could be ascertained from its circuit just why the Transistorised Playmaster had such a dreadful frequency response and measures so badly.
Ever since its review in 1966, I’ve wondered how Fidelity could have made such an awful tape recorder, and actually submitted it for a technical review!
I hope we can find out. The circuit appears to be fairly conventional. If so, can it be improved with a different choice of components?

Tony.
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Old 8th Jan 2022, 2:26 pm   #46
Ted Kendall
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

Perhaps they just took the Mullard circuit and omitted anything to do with the speed change switch?
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Old 8th Jan 2022, 3:49 pm   #47
david freeman
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

It still doesn’t explain why the frequency response was so diabolically poor.
The valve Playmaster certainly manages to record frequencies up to 8khz, and which are audible through its speaker, although bass is very limited.
However, connected to a decent system, there is bass from around 80hz.
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Old 13th Jan 2022, 11:33 am   #48
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

Just a running report.

To cut a long story short, I found one dud transistor in the output pair so replaced both, and tested all the others. Replaced the BC109 input transistor by the correct BC107 although it tested OK, and while I was at it replaced the metal rectifier by a diode bridge, plus new smoothing caps. 23v. measured at rectifier output. Result, no sound at all..... Found an o/c resistor in the supply to the emitter of BC107 and replaced it. We now have audio all the way through with volume and tone controls working, more gain than before but still not enough. Sound is much as would be expected from an uncased internal speaker, but not enough gain to assess it properly.

At the input transistor, I am seeing 15v at the base, 16.5v at the emitter and 3.5v at the collector. Surely this is much too high at the base? The Playmatic diagram which is similar gives 4.5v, 10v and 2.5v respectively, so the others are at least in the right region.

So a bit of progress, but it is a frustrating thing to work on as the wiring to the deck is too short to allow the board to be pulled out conveniently.
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Old 14th Jan 2022, 6:13 pm   #49
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

Might be worth re-replacing the BC107 just in case. I'd have thought a BC109 would have done the job so might have been the original.
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Old 14th Jan 2022, 6:58 pm   #50
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Might be worth re-replacing the BC107 just in case. I'd have thought a BC109 would have done the job so might have been the original.
The BC109 had the RS logo so was clearly a replacement but yes, it would probably work and might be worth a try. I thought it best initially to revert to original as far as possible.

Since then I have had another session on it and changed a few more resistors, and it is now working at least in principle.

Playback at acceptable volume but yes, it sounds dreadful! Both through the internal speaker, and external amp via monitor socket. Just very tinny - masses of treble, the bass is audible but just not coming through.

Recording tried very crudely. Only the mic input is working, but I plugged my phono output into it and it certainly recorded, it also erased, and the level indicator responds so the deck switching appears to be OK.

The deck is surprisingly quiet and smooth for a TD2.

Time to have a think about it, as I am reaching the limits of my knowledge.
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Old 16th Jan 2022, 11:45 am   #51
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

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At the input transistor, I am seeing 15v at the base, 16.5v at the emitter and 3.5v at the collector. Surely this is much too high at the base? The Playmatic diagram which is similar gives 4.5v, 10v and 2.5v respectively, so the others are at least in the right region.
All these look wrong to me! But the 15, 16.5, 3.5 looks less wrong than the other. For a conducting Si transistor the base-emitter voltage should be about .6 or .7 of a volt.

Is there a decoupling capacitor across the emitter resistor of the BC107/9? (Could be actually across the emitter resistor or could go to anywhere that is earthy to AC). If that C is low capacitance it could easily cause low gain.
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Last edited by Cobaltblue; 16th Jan 2022 at 12:10 pm. Reason: fixed quote
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Old 16th Jan 2022, 12:02 pm   #52
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All these look wrong to me! But the 15, 16.5, 3.5 looks less wrong than the other. For a conducting Si transistor the base-emitter voltage should be about .6 or .7 of a volt.

Is there a decoupling capacitor across the emitter resistor of the BC107/9? (Could be actually across the emitter resistor or could go to anywhere that is earthy to AC). If that C is low capacitance it could easily cause low gain.
Graham
Thankyou. I think it must be something of that sort, will have a look later.

Last edited by Cobaltblue; 16th Jan 2022 at 12:13 pm. Reason: Even bigger quote fix
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Old 16th Jan 2022, 8:01 pm   #53
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

The decoupling cap. in fact appears in the photo in post 26 and is marked 6.4u.and measures 7u. Other caps and resistors in this area of the board check OK.

Reinstated the BC109. This has made little if any difference to anything, but it can stay put as the pcb tracks are very delicate in this area.

I may well have missed something obvious. I think the input stage is working properly, because setting the tone control to max. treble produces distortion on the speaker which sounds like the rated 3 watts, which surely would not happen if the initial gain was too low.
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Old 16th Jan 2022, 11:44 pm   #54
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

I agree with Graham, those voltages look nothing like what one would expect. Even the voltages given in the service sheet look crazy.
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Old 17th Jan 2022, 1:16 am   #55
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Gentlemen,

If the service sheet isn't reliable then I am wasting my time with this, and I would be very happy to pass it on to someone who knows what they are doing.

Tony.
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Old 17th Jan 2022, 1:57 pm   #56
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

What a shame.
I was hoping for a solution as to why the Transistorised Playmaster had such a dreadful performance when the valve version was at least competitive within its price range.
A frequency response of 400 to 3000hz would have been painfully obvious even to the most casual listener.
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Old 17th Jan 2022, 3:05 pm   #57
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What a shame.
I was hoping for a solution as to why the Transistorised Playmaster had such a dreadful performance when the valve version was at least competitive within its price range.
A frequency response of 400 to 3000hz would have been painfully obvious even to the most casual listener.
Me too! The thing needs to be stripped out of the case/deck assembly and thoroughly "looked at" with good test gear. It wasn't difficult or expensive in the discrete silicon era to produce a decent-sounding transistorised tape amp. So, for heavens sake, what did Fidelity do to it?

Mike
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Old 17th Jan 2022, 4:06 pm   #58
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

I think the problem was that the tape recorder was probably the most expensive and under used bit of electronic kit to ever enter the domestic domain.
Most were played with for a couple of hours maybe recording records through a microphone with disastrous results. They were then put away in a wardrobe for decades.

I think Fidelity went down this path simply satisfying a 'novelty' market the attraction of which soon wore off!
There were some very good domestic recorders produced particularly from Thorn and models using the BSR TD2 series deck such as the Elizabethan and many more. Some models an example of which is the Grundig, cost as much as a TV receiver but sold in large numbers but I doubt if most had more than a few hundred hours use. John.
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Old 17th Jan 2022, 5:09 pm   #59
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Default Re: Fidelity transistorised Playmaster - reverse engineering?

And yet, Fidelity produced the Playmaster Major, which was also reviewed by Alec Tutchings in the Tape Recorder, and H Burrell Hadden in Tape Recording Magazine, and it received really excellent reviews with its correct speed equalisation, excellent frequency response, and better than average sound quality. They clearly knew how to design a decent tape recorder.
So why make such a pigs ear of the transistorised Playmaster, and submit it for review knowing that it would be instantly slated on every part of its design or lack of?

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Old 17th Jan 2022, 6:53 pm   #60
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And yet, Fidelity produced the Playmaster Major, which was also reviewed by Alec Tutchings in the Tape Recorder, and H Burrell Hadden in Tape Recording Magazine, and it received really excellent reviews with its correct speed equalisation, excellent frequency response, and better than average sound quality. They clearly knew how to design a decent tape recorder.
So why make such a pigs ear of the transistorised Playmaster, and submit it for review knowing that it would be instantly slated on every part of its design or lack of?
I suppose the extraordinary decision not to include any equalisation circuitry (see post #15) would explain a lot of the shortcomings. The other thing that doesn't seem to have been investigated so far on this thread is the record-head bias. Inadequacy there would also explain the symptoms. I wonder if the OP has tried playing a decent tape recorded on another, working machine...

Mike
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