Fidelity transistorised Playmaster - reverse engineering?

[Boulevardier]

Don't know if anyone has checked, but I wonder if there was any recording-mode equalisation used. Perhaps there was no equalisation for either mode. Maybe Tutchings covered this.

[Borderer]

The very concise review is in here. https://worldradiohistory.com/Archiv...nd-1966-08.pdf

[DMcMahon]

Obviously a lot of interest going by the high number of Thread views, I find it interesting.

David

[Borderer]

My new example is in better condition than the last one, clean and unmolested inside and seems substantially original. At first glance there are minor differences in the PCB, but will have to compare it carefully with earlier photos. It has HT, mains hum through the speaker, but no audio, so we will see.

Will upload some pictures asap.

Tony.

[Borderer]

Photos attached

[ben]

Mine had a dead output stage, not even hum. Maybe next month I will take another look. Will upload pics for comparison.

[Ted Kendall]

Looks the same to me. Does it have a spare way on the rec/rep switch? Random thought - did the transistor machine precede the valve version? It could just be that, faced with an intractable problem, Fidelity just "ran home to Mama" and used valves instead, After all, the later Braemar did, didn't it?

[Borderer]

Originally Posted by Ted Kendall

Looks the same to me. Does it have a spare way on the rec/rep switch? Random thought - did the transistor machine precede the valve version? It could just be that, faced with an intractable problem, Fidelity just "ran home to Mama" and used valves instead, After all, the later Braemar did, didn't it?

There is a spare position on the r/p switch. Haven't studied it all properly yet.

AFAIK the valve version came first in about 1964 and continued after the transistor one was dropped, then as you say the Braemar used valves. They do seem to have got cold feet about transistors although there was another model - Playmatic? which was a transistor/valve hybrid.

[Restoration73]

I still have my original TR5 (valve) version, and limitations of the transistor type shown
must surely be down to the early design - although Philips were making an all transistor
design by this time. Moving forward a few years a fully transistor design (based on a
Mullard circuit) used only 6 transistors e.g see p44 of this PW tape recorder project;

https://worldradiohistory.com/UK/Pra...PW-1971-12.pdf

[Ted Kendall]

Given that the follow-up to the Tutchings review didn't appear and that other transistor examples don't differ much, if at all, I think Fidelity just gave it up as a bad job. Which isn't to say that it can't be improved, but the topology is awkward.

[Ted Kendall]

Originally Posted by Restoration73

I still have my original TR5 (valve) version, and limitations of the transistor type shown
must surely be down to the early design - although Philips were making an all transistor
design by this time.

Undoubtedly the components and knowledge existed, just not at Fidelity.

[Borderer]

The footnote to the Tutchings review may perhaps have just been a bit of editorial diplomacy. I guess in production terms a revision would have meant a new pcb and it may not have been economic. But it doesn't explain how they got it so wrong in the first place.

[Boulevardier]

Originally Posted by Borderer

But it doesn't explain how they got it so wrong in the first place.

Nor why, given that they must have known it was rubbish, they let it out onto the market under the Fidelity brand name. That's what I find really baffling. Suggests a catastrophic breakdown in design, product development, and quality control systems.


Mike

[Ted Kendall]

Depends on what you mean by "rubbish" - perhaps they thought they could get away with it at that price point, although the earlier Argylls and such were decent enough budget machines. Maybe it was the work of some bright young thing who left before he finished the design - who knows, after all this time?

[Cobaltblue]

Sometimes an external influence means you are forced down a path you know to be a problematic

Back in the early 90's we developed a product where HQ wanted to use a particular architecture. The engineering team thought the technology immature, and so it proved. It was a disaster, sales fell off a cliff and it put us on the back foot to replace it after a year where as typical product cycle was between 8 and 10 years.
The problems were immediate and at that time unsolvable with the existing hardware.
Our current products use very similar architecture but developed 15 years later when it was mature.

It did a lot of damage to our reputation.

The same may have been true at Fidelity.

The salesman all wanted to bandy around the title "transistor" when the development team had insufficient expertise and resource to succeed.

Such things are happening somewhere even now.

Cheers

Mike T

[Borderer]

The situation may well have been something like Mike T describes.

The PW design referenced in post 173 makes interesting reading, to me at least, and I wonder how it would compare with the Fidelity in practice.

[Chris55000]

I have now just acquired a complete 4 Track Transistorised Playmaster today, along with a smashed case because the courier dropped it, but I'm hoping the PCB survived intact, but at least I will have all the original transformer, motor and all the associated wiring and switching I need to complete my diagram completely and correctly!

(It is now ¾ done but temporarily put on one side for other Member's projects currently in progress!)

Chris Williams

[ben]

First post/repair of 2023 and I hope this doesn't hint at what's to come!!

I'm bumping this as I have dug out my transistorized playmaster, an ebay purchase from some time ago which got put away in favour of other more pressing stuff.

Unfortunately, it has been got at.

- The loudspeaker leads were disconnected.
- There is no mains smoothing capacitor(s) or rectifier (removed)
- Some 2-legged component is missing that connects to one of the output transistors and ground - resistor I assume

Symptoms are no audio whatsoever and the magic eye heater is on but the green part does not come on when record is selected.

There is some 16v reaching the main pcb from the transformer, presumably the supply for the audio stages.

I'm tempted to strip this for spares but I'll at least try fitting a smoother/rectifier.

[david freeman]

Looking forward to your next post on this!

[ben]

Perhaps someone reading this could confirm something. From the diagram in post 18, am I to assume that the positive output from the rectifier is in fact fed to chassis and the negative to the output stage? Or is that diagram for a different setup?

Since the entire rectifier was removed and there are no board markings, I'm largely in the dark.