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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 1st Jul 2022, 2:18 pm   #1
JoeZenit
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Default ELPICO TR500 component identification

I have recently acquired an ELPICO TR500 which works fine except for volume decreasing as it gets hotter. Whilst having a look I found a destroyed WIMA 2200pF 1000v 500v 250v XX(b) 100Cm 10% capacitor attached to the speaker transformer. As I am new to Valve circuits and the high voltages i don't know what I should be trying to find to replace it. I can't seem to find anything close. Can anyone help?
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Old 1st Jul 2022, 5:05 pm   #2
DMcMahon
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Default Re: ELPICO TR500 component identification

Hello Joe and welcome to the Forum.

I have recently changed a very similar Wima capacitor, mine had 2 voltage ratings 1,000V and 500V, the higher voltage is the AC voltage rating I think, it is not directly relevant here but there is formula for converting AC voltage to DC, namely AC voltage divided by the square root of 2 (1.41) = DC voltage.

See Post # 6 of my linked Thread where mine is C30.

https://www.vintage-radio.net/forum/...d.php?t=192169

Not sure why yours has a third voltage rating.

The capacitor across the output transformer primary often will have a AC voltage rating stated, whereas most standard capacitors often will only have a DC voltage rating.

Your 2,200pF (2,200 picofarad) is the same as 2.2nF (2.2 nanofarad), also the same as 0.0022uF (0.0022 microfarad).

I prefer to use Polypropylene capacitors but any modern good quality Polyester, Ceramic etc will suffice, I would say of at least 500V DC for the output transformer. I use 630V DC rated capacitors.

It is not that easy to find higher rated DC voltage rated capacitors (Ceramic disk being one exception) and also not that easy to find ones with a specific AC rating.

Are you saying it is destroyed because of its visual condition or does it measure bad.

These old Wima capacitors do often degrade and become electrically leaky so is best to replace them.

A new/modern replacement will be quite a bit smaller in physical size.

David

Last edited by DMcMahon; 1st Jul 2022 at 5:16 pm. Reason: Updated capacitor values
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Old 1st Jul 2022, 5:44 pm   #3
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Default Re: ELPICO TR500 component identification

Should have mentioned that there is a potential issue if the grid coupling capacitor to the output valve (which drives the output transformer) becomes leaky then it can allow DC voltage to pass through the capacitor and stress the valve and transformer and worst case lead to permanent damage.

These coupling capacitors on this vintage of machine will often will be paper/waxy capacitors that can suffer with this problem.

If you can do it safely and can identify the control grid of the output valve then measure it (DC voltage selected on test meter) with respect to ground, to make sure there is no +ve DC voltage present. If any doubt then just replace the capacitor.

David
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Old 1st Jul 2022, 6:34 pm   #4
1955APREN
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Default Re: ELPICO TR500 component identification

Hi Joe
I agree with all David as said in the last 2 post . Could you please let us
know what test equipment you have ie test meter ect. The capacitor is often
know as tone corrector to reduce the top frequency of the output stage.
I have 2.2nf rated at 1600v . It is a MKP type , this will be ok for a replacement , but you will have to extend the leads , just solder two pieces
of wire to each leg and slide some sleeving over the joints.
If you send me PM with your name and address I will post it to you FOC.
Regard
Derrick
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Old 1st Jul 2022, 7:12 pm   #5
Lucien Nunes
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Default Re: ELPICO TR500 component identification

Quote:
mine had 2 voltage ratings 1,000V and 500V, the higher voltage is the AC voltage rating I think
Just to clarify, the AC rating is invariably lower than the DC rating.
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Old 1st Jul 2022, 7:58 pm   #6
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Default Re: ELPICO TR500 component identification

On this YouTube clip of the TR500 the same fault is reported and the 2,200pF is found to be in a mess, but this clip does not cover the replacement, i.e. not known from this clip if new capacitor fixed the issue.

https://www.youtube.com/watch?v=bVDfAE3H6A0

David

Edit update - At the end of the clip he did recording with the bad capacitor removed and said it worked the best it ever has. He earlier had said something like the transformer was shared or used by the record head, I did not really understand this part and not sure if he was correct or not.

Last edited by DMcMahon; 1st Jul 2022 at 8:05 pm. Reason: Update
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Old 1st Jul 2022, 8:27 pm   #7
Maarten
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Default Re: ELPICO TR500 component identification

Quote:
Originally Posted by Lucien Nunes View Post
Quote:
mine had 2 voltage ratings 1,000V and 500V, the higher voltage is the AC voltage rating I think
Just to clarify, the AC rating is invariably lower than the DC rating.
And often also lower than the DC rating divided by 1.41 (in this case it's a factor 2). If not given, it should be assumed to be the DC rating divided by 2.82. This is often a bit too conservative, but it's essentially what the capacitor will see when it retains charge during a fast reversal of polarity.

Another useful rule of thumb, is that a (paper) capacitor that is somehow attached to a large coil or transformer, should be replaced with a polypropylene capacitor as it could see large inductive pulses.
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Old 1st Jul 2022, 9:41 pm   #8
DMcMahon
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Default Re: ELPICO TR500 component identification

From the YouTube TR500 example I see that some of the capacitors are Hunts, these like Wima have quite a bad reputation of becoming leaky when old.

Also note that the grid coupling capacitor potential issue can also apply to other parts of the circuitry prior to the output valve, although with not so much potential for component damage.

I wonder if the coil/other transformer next to the output transformer he is talking about is for the bias oscillator.

I cannot easily find a schematic for the TR500.

David
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Old 2nd Jul 2022, 2:15 am   #9
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Default Re: ELPICO TR500 component identification

I had an Elpico like that and I seem to remember having to replace about five capacitors to get it fully operational. If the grid coupling capacitor isn't replaced and it's left running for any length of time like that it'll end up in melt down!
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Old 2nd Jul 2022, 9:02 am   #10
DMcMahon
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Default Re: ELPICO TR500 component identification

Quote:
Originally Posted by 1955APREN View Post
Hi Joe
I have 2.2nf rated at 1600v . It is a MKP type , this will be ok for a replacement , but you will have to extend the leads , just solder two pieces
of wire to each leg and slide some sleeving over the joints.
I would snap up this kind and generous offer, it will save you having to choose which one/type to order.

It is well rated and being MKP (a metalized polypropylene film type) it is ideal.

David
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Old 2nd Jul 2022, 11:29 am   #11
JoeZenit
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Default Re: ELPICO TR500 component identification

Thank you for all the posts. It's the first time I've tried to fix a valve unit (and therefore all the high voltages) and didn't want to make a terrible mistake with this component and cause damage to what is otherwise a good machine.
I have taken the offer of the capacitor and will replace it, test the machine and then proceed with the other advice offered.
It is also the first Forum I have tried to use so thank you all.
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Old 4th Jul 2022, 12:01 pm   #12
DMcMahon
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Default Re: ELPICO TR500 component identification

Quote:
Originally Posted by DMcMahon View Post

I cannot easily find a schematic for the TR500.

David
I now see that the TR500 is covered in Hellyer's "Tape Recorder Servicing Handbook".

It does not have a schematic for the TR500 but states that it is electrically the same as the TR600 (there is a schematic for that) without the track switching (TR600 being 4 track) and without the transistor preamp, it also says that the TR500 may have a 50uF capacitor across resistor R9.

The original capacitor in question is identified as C16 on the TR600 schematic.

Davids
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Old 7th Jul 2022, 8:39 pm   #13
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Default Re: ELPICO TR500 component identification

Quote:
Originally Posted by Maarten View Post
[Another useful rule of thumb, is that a (paper) capacitor that is somehow attached to a large coil or transformer, should be replaced with a polypropylene capacitor as it could see large inductive pulses.
Maarten, out of interest how would a HV Ceramic disc capacitor compare to a Polypropylene in this application where large inductive pulses would be present ?

David
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Old 18th Jul 2022, 9:24 am   #14
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Default Re: ELPICO TR500 component identification

The TR600 schematic is available for download from the Forum "Instant Downloads".

David
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