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Question HMV 2208; Replacement/Equivalent Cap

 
Spike47
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Can anyone recomend a replacement/equivalent Cap for a "Hunts" 0.003uF 300Vac Capacitor .
It is from a HMV 2208  Reel to Reel Tape Recorder "Hunts" (the manufacturer) 0.003uF 300Vac capacitor connected across the audio output transformer's primary winding

Cheers

Spike

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Topic starter Posted : 27/04/2021 5:36 pm
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Spike47
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Schematics Screen shot Schematic 2 clipped.pngScreen shot Schematic 1 clipped.pngScreen shot Schematic 3.png

 

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Topic starter Posted : 27/04/2021 5:45 pm
Cathovisor
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Search the Internet for 3300pF/3.3nF at 1000V DC polypropylene film capacitor.

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Posted : 27/04/2021 7:37 pm
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Spike47
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@cathovisor

 

Thank you

 

Spike

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Topic starter Posted : 27/04/2021 8:07 pm
Spike47
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Posted by: @cathovisor

Search the Internet for 3300pF/3.3nF at 1000V DC polypropylene film capacitor.

Hi

Can only find 630v type Cap .

 

cheers

Spike

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Topic starter Posted : 27/04/2021 8:19 pm
crustytv
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Posted by: @spike47

Can anyone recomend a replacement/equivalent Cap for a "Hunts" 0.003uF 300Vac Capacitor .

When replacing caps, follow these basics.

Capacitance; replace with like for like or the modern equiv value e.g .05uF(old) .047uF(new)

Voltage general rule of thumb; same voltage or higher is OK, but never lower.

When VAC is stated, multiply this by 3 for VDC. This is why Catho stated 1000VDC. 300VAC x 3 =900VDC which you will not find, so 1kV (1000VDC) is what you need. Keep looking and try the big outlets RS & Farnel etc.

 

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Posted : 28/04/2021 7:51 am
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Nuvistor
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Spike47
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Posted by: @nuvistor

https://www.cricklewoodelectronics.com/C2K3N3.html

or parallel these.

https://www.cricklewoodelectronics.com/CAT1N0.html

https://www.cricklewoodelectronics.com/2200pF-1500V-Polypropylene-Axial-Capacitor.html

I would probably use the first item.

Hi

Paralleling them both you mentioned would be the cheapest method, would I be good to go on that ?

spike

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Topic starter Posted : 28/04/2021 10:34 pm
Nuvistor
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I would use this,

https://www.cricklewoodelectronics.com/C2K3N3.html

It will be cheaper, smaller and easier to fit. I mentioned the others in case you didn’t want to use ceramic.

The type above will do the job for less than £1. At first glance it’s a tone correction capacitor so not too stringent a job apart from requiring a high working voltage.

 

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Posted : 29/04/2021 7:36 am
Spike47
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Posted by: @nuvistor

I would use this,

https://www.cricklewoodelectronics.com/C2K3N3.html

It will be cheaper, smaller and easier to fit. I mentioned the others in case you didn’t want to use ceramic.

The type above will do the job for less than £1. At first glance it’s a tone correction capacitor so not too stringent a job apart from requiring a high working voltage.

 

Hi

Thanks for your reply, yeh not sure about the ceramic one, dosen't look like it will hold much capacitance, if that is the correct phrase to use !.

Cheers

Spike

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Topic starter Posted : 29/04/2021 8:29 am
Spike47
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@crustytv

Thank you for that info.

Cheers

Spike

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Topic starter Posted : 29/04/2021 8:32 am
Nuvistor
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The capacitor is there to bypass higher audio frequencies, as the audio frequency increases the capacitive reactance will reduce,. Eg at 1000hz it’s reactance is around 48k ohms, at 10000hz it’s around 5k ohms. This will reduce the higher audio frequencies being passed through to the speaker and make the sound more mellow. Some manufacturers would put a variable resistor in series with the capacitor and have an adjustable “ Tone control” on this recorder it is fixed.

The requirement for a high voltage capacitor is the possibility of high voltage spikes on the audio transients.

Any comments and corrections appreciated, it’s a long time since I did this sort of thing.

 

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Posted : 29/04/2021 9:14 am
Spike47
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Posted by: @nuvistor

The capacitor is there to bypass higher audio frequencies, as the audio frequency increases the capacitive reactance will reduce,. Eg at 1000hz it’s reactance is around 48k ohms, at 10000hz it’s around 5k ohms. This will reduce the higher audio frequencies being passed through to the speaker and make the sound more mellow. Some manufacturers would put a variable resistor in series with the capacitor and have an adjustable “ Tone control” on this recorder it is fixed.

The requirement for a high voltage capacitor is the possibility of high voltage spikes on the audio transients.

Any comments and corrections appreciated, it’s a long time since I did this sort of thing.

 

Hi

Thanks for that info, the Cap question came originaly because the Tape has a very low vollume and someone suggested this Cap ! .

 

Cheers

Spike

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Topic starter Posted : 29/04/2021 9:26 am
Nuvistor
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Well if the capacitor had a high leakage it could reduce the volume but I suggest some standard fault finding. Disconnect one end and test it, the recorder will work without it but have more treble. You will probably find it’s other faults that are causing the low volume, presume the tape heads are clean and not badly worn.

What test equipment have you?

 

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Posted : 29/04/2021 9:40 am
Spike47
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Posted by: @nuvistor

Well if the capacitor had a high leakage it could reduce the volume but I suggest some standard fault finding. Disconnect one end and test it, the recorder will work without it but have more treble. You will probably find it’s other faults that are causing the low volume, presume the tape heads are clean and not badly worn.

What test equipment have you?

 

Hi

Thanks for your reply, just a Digi Multimeter I am afraid !.

Cheers

ps: Yes I think I will remove that Cap to see if that makes any difference, could be a resistor now with its age !. 

Spike

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Topic starter Posted : 29/04/2021 10:11 am
Nuvistor
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@spike47

No point guessing, you could change many items and not find the fault. 

Are you capable of safely taking voltage readings? If you are then that is one way to start, there are other ways but that would be a guide.

Do you know how the tape recorder works, what each stage does? A basic understanding helps to fault find.

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Posted : 29/04/2021 10:44 am
Spike47
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Posted by: @nuvistor

@spike47

No point guessing, you could change many items and not find the fault. 

Are you capable of safely taking voltage readings? If you are then that is one way to start, there are other ways but that would be a guide.

Do you know how the tape recorder works, what each stage does? A basic understanding helps to fault find.

Hi Frank

Thanks for your reply I wasn’t guessing a member on here suggested that , I was an Electrician in my earlier life 😊

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Topic starter Posted : 29/04/2021 11:00 am
Nuvistor
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@spike47
it was the comment about it could be a resistor that gave me cause for concern.

No harm in trying the capacitor but if you that doesn’t fix the fault then a standard fault finding technique would hopefully find the problem.

 

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Posted : 29/04/2021 11:03 am
Spike47
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Posted by: @nuvistor

@spike47
it was the comment about it could be a resistor that gave me cause for concern.

No harm in trying the capacitor but if you that doesn’t fix the fault then a standard fault finding technique would hopefully find the problem.

 

Hi Frank 

Thanks again for your reply, that bit about a resistor was also from a member in this post, will print out schematic and do some testing .

thank you again for sharing your time and knowledge .

Cheers

Spike

 

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Topic starter Posted : 29/04/2021 11:08 am
Nuvistor
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@spike47
The manual has a good circuit description if you understand the basics. Voltage readings and signal injection should easily find a fault in the playback amplifier if that’s where the fault resides.

 

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Posted : 29/04/2021 11:11 am