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Old 3rd Nov 2012, 4:57 pm   #1
vampyretim
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Default Dansette Bermuda, resistor help.

Hi guys,

Can somebody please clear up for me what component this is, is it a resistor or a very small value capacitor?

I would of (have) thought the 1.8k meant ohms but I just want to be certain.

Many thanks.
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Old 3rd Nov 2012, 5:00 pm   #2
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Default Re: Resistance help.

Looks like a 1800pF ceramic tubular capacitor to me.

Cheers

Mike T
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Old 3rd Nov 2012, 5:02 pm   #3
G8HQP Dave
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Default Re: Resistance help.

Yes.
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Old 3rd Nov 2012, 5:05 pm   #4
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Default Re: Resistance help.

Thanks a lot Mike,

It's sticky and cracked and was in series with a 180 ohm resistor to pin 7 of an EL84 in a Dansette Bermuda.

I have replaced the .04 coupling cap you can see and am going to put a 1/2 w carbon resistor in place of the pathetic looking 1/4 w one you see in the pic.

Does anyone know of suitable modern replacement for the 1800pF cap?
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Old 3rd Nov 2012, 5:19 pm   #5
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Default Re: Resistor help.

Increasing the Value to 0.04 will increase the top cut.

This capacitor is between the Anode and the Cathode. The resistor is the Bias resistor in the Cathode circuit.

This capacitor should have an adequate voltage rating as very high peak voltages can appear across it.

I would use a 1000V component here.

As far as I know 1800pF is still a preferred value so you should be able to get a replacement.

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Old 3rd Nov 2012, 10:30 pm   #6
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Default Re: Resistor help.

If you have any difficulty getting an 1800pF aka 1.8nF or 0.0018uF capacitor in a suitably robust high voltage type, you may find 2200pF/2.2nF easier to find.

With that small increase, the tonal difference in a simple top cut circuit like this would not be much, but as an earlier contributor said, 0.04 (uF) or 40nF/40000pF is really a lot bigger.
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Old 3rd Nov 2012, 11:07 pm   #7
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Default Re: Resistor help.

Quote:
Originally Posted by vampyretim View Post

I would of (have) thought the 1.8k meant ohms but I just want to be certain.

Many thanks.
'k' means 1000 (kilo) so it doesn't matter if it's used on a resistor or a capacitor.
So it can represent 1,000 ohms or 1,000pF.

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Old 4th Nov 2012, 12:17 pm   #8
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Default Re: Resistor help.

I repaired one of these some time back. The same components on mine had failed; one section of the big multi cap, the rectifier, 'your' cap and the 1800pF cap as well as the anode resistor going high.

I found some resistors were different to the ones shown on the circuit. Still, a nice simple little amp.

Andy.
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Old 5th Nov 2012, 11:16 am   #9
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Default Re: Dansette Bermuda, resistor help.

Hi guys,

I have ordered some 1800pf 630v caps from Just Radios, thanks for your help.

I think my wording in a previous post may of been a bit confusing, I didn't mean to say that I was replacing the 1800 pf cap with a .04 UF one. I meant that in the pics I posted there's a big yellow coupling cap that goes to the output transformer, I have replaced that cap with a .047 UF one.

Someone has had a go at repairing this in the past and replaced the cathode bias resistor with one of a lower power dissipation, the other power supply resistor 3.3k is original.

I have replaced the smoothing can too.

I have learnt the theory of valve amps from books and my grandfather I've been learning for about 18 months now and it's great fun finally putting it into practice, I built a lamp limiter a few weeks back and am very grateful for the help this website and it's members provide.

Thanks again guys,
Tim.
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Old 9th Nov 2012, 2:58 pm   #10
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Default Re: Dansette Bermuda, resistor help.

Hi guys,

just an update have a few pics for you all to have a look at.

I haven't replaced the selenium rectifier yet as I don't know what value of wire wound resistor to replace it with as my AVO 8 isn't working and am waiting on it to be repaired.

I turned on the Dansette though with a lamp limiter and it all seems fine. I played a sacrificial record and it sounds lovely.

Thanks for all your help.
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Old 9th Nov 2012, 7:22 pm   #11
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Default Re: Dansette Bermuda, resistor help.

Just a couple of quick questions, I have measured the voltage of the selenium rectifier and it's a steady 240 volts, is it still good practice to replace as a matter of course?

Also I have noticed the light bulb indicating the unit is on is fluctuating ever so slightly in brightness, does this indicate a problem with the mains transformer?

Many thanks.
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Old 9th Nov 2012, 8:10 pm   #12
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Default Re: Dansette Bermuda, resistor help.

Personally I always replace selenium rectifiers with silicon 'on sight', on the basis that sooner or later an apparently good one will fail.
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