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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 15th May 2020, 3:51 pm   #41
ChrisChilton
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Default Re: Tellux record player

Yes!
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Old 15th May 2020, 4:00 pm   #42
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Default Re: Tellux record player

Great - that simplifies things!
Common problem. These transistors tend to develop an internal short to case. When clamped together to metal, current goes where it should not go, usually to ground.

In the past as a bodge I have made new, individual heat sinks for them so as to isolate them, but in the long term is it advisable to replace like for like.

Look for numbers, something like 'AC187'.
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Old 15th May 2020, 4:03 pm   #43
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Ac128
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Old 15th May 2020, 4:29 pm   #44
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Default Re: Tellux record player

Ah, that's one then. What's the other heatsunk one? AC176? And the other one in the middle of the board?

At least there's no ICs made from unobtanium, you can probably get suitable replacement transistors without too much difficulty or expense.
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Old 15th May 2020, 5:03 pm   #45
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Default Re: Tellux record player

There will be enough volts around so that a small twiddle to the bias will allow silicon devices to replace germanium if need be.

The photo in the earlier thread shows two epoxy-on-ceramic cased small transistors as the earlier stages. Those could well be Si.

The point I tried to make earlier is to find out about live chassis first before anything is touched. In this case it was safe, but it's definitely preferable to do these things in the right order, and to explain to beginners.

The amplifier may well be held in by the nuts on the pot bushes.

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Old 15th May 2020, 5:27 pm   #46
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Default Re: Tellux record player

as Mike T (Cobaltblue) said earlier - this thread https://www.vintage-radio.net/forum/...d.php?t=101469 is the very same record player. It is a fairly simple amplifier - I remember 'improving' it by beefing up the power supply (fullwave rect) and replacing some caps.

I can't recall all the details (it was a while ago!), but I'll get it out if you think it will help - I normally only get it out to play my 45 collection (mainly 1960s/70s). I have to say, it works and sounds much better than I thought it would!

Tracking down replacement transistors can be difficult, so it may be easier to substitute a modern amp, keeping the volume and tone controls.
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Old 15th May 2020, 6:06 pm   #47
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It looks very similar to your player but the pcb is slightly different I think. Happy to accept any and all advice, I just want it to work to play 45s from the same era as yourself.
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Old 15th May 2020, 9:12 pm   #48
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Quote:
Originally Posted by ben View Post
Great - that simplifies things!
Common problem. These transistors tend to develop an internal short to case. When clamped together to metal, current goes where it should not go, usually to ground.

In the past as a bodge I have made new, individual heat sinks for them so as to isolate them, but in the long term is it advisable to replace like for like.

Look for numbers, something like 'AC187'.
So what do I need to do next? Get some replacement transistors?
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Old 15th May 2020, 9:21 pm   #49
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Default Re: Tellux record player

You can either replace the transistors or use separate heat sinks as Ben suggested.

A Good place to buy Germanium transistors is here :

https://www.cricklewoodelectronics.com/AC128.html

There is a good chance you will need to replace some of the electrolytic capacitors as well, they may well now have gone low capacitance.

Do you have a soldering iron and a Meter?

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Old 15th May 2020, 9:36 pm   #50
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Default Re: Tellux record player

Thanks Mike.

Turns out that one is an AC128 and the other is an AC176.

Good job I checked before ordering.
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Old 15th May 2020, 9:36 pm   #51
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Quote:
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Do you have a soldering iron and a Meter?
I have a meter and need to get a soldering iron now I feel.
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Old 15th May 2020, 9:49 pm   #52
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You'll need some flux cored electronics solder wire too. Try to get hold of the "full fat" 60% tin 40% lead stuff, it's easier to work with and is what would have been used originally anyway.

(It's no longer permitted to be used for every day electronics production so as to keep the lead in scrap stuff out of the environment)
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Old 15th May 2020, 11:52 pm   #53
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If you decide to change the transistors, Make very careful notes of what pins go where, especially the red dot on the cans.
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Old 15th May 2020, 11:56 pm   #54
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Default Re: Tellux record player

One 'bodge' that has worked for me in the past is to wrap some thin sellotape around the transistor just one layer, this electrically insulates the can from the heatsink but still allows the heat to be dissipated.

Cheaper than new transistors and the ones Cricklewood sell are slightly different tothe ones you have in that the can is more like a TO18 and has a slightly smaller diameter than the original.
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Old 15th May 2020, 11:57 pm   #55
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Quote:
Originally Posted by ben View Post
If you decide to change the transistors, Make very careful notes of what pins go where, especially the red dot on the cans.
Would you recommend that I change the transistors rather than attempting to heat sink them?
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Old 16th May 2020, 12:02 am   #56
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Quote:
Originally Posted by Michael Maurice View Post
One 'bodge' that has worked for me in the past is to wrap some thin sellotape around the transistor just one layer, this electrically insulates the can from the heatsink but still allows the heat to be dissipated.

Cheaper than new transistors and the ones Cricklewood sell are slightly different tothe ones you have in that the can is more like a TO18 and has a slightly smaller diameter than the original.
Tape around both transistors or just one?
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Old 16th May 2020, 12:16 am   #57
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Default Re: Tellux record player

Since you don't know which one (or maybe both ) is/are leaky, wrap the two of them as Michael says. See how it goes from there.
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Old 16th May 2020, 12:20 am   #58
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Default Re: Tellux record player

So it was the old 'tin whisker' problem after all, and also not an IC amplifier as had been suggested, so that's a relief. You could check which one of the transistors has the 'whiskers' with your meter set to a low ohms range to see which one has a short to its case, it could be both of them of course. I'd recommend the Sellotape bodge for ease of repair, as NOS replacements may well be just as bad - or very soon will be.
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Old 16th May 2020, 12:26 am   #59
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What can I say?

Sellotape!

It worked!

Thank you so much, I can’t express how grateful I am.

I assume that the buzzing will dissipate when I connect it back to the metal plate inside the cabinet rather than it grounding through me.
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Old 16th May 2020, 10:35 am   #60
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Default Re: Tellux record player

Let us know......

There may be other tired components still to be found and replaced!
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