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While I was changing out a signal tube socket, I broke what I believe to be a Zener Diode. I've attached a picture showing my good channel with 2 joined (Diode?) pairs abutting the socket. In the upper right hand of the picture I photo-shopped in the damaged pair, where unfortunately a wire broke off inside one of them.
The parts are clear encased, with TRW H56 on them, and looks like a red band identifier.
If indeed they are the parts I think they are, then the manual describes them as 1N5274B, 1/2W, 130V, 5%.
One question is have I identified this part correctly?
Also, do I really need to put two together, or might I be able to find one value that would equal the pair. Not sure how to calculate this or maybe there was a distinct reason for using a pair?
Sadly, if I have identified them properly, it doesn't look like they are in stock at Mouser, but on order. Oh well.
Any help would be appreciated.
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Follow Ups:
nt
The schematic called for 27pf 2%. I could only find 5% in either 27pf or 56pf. Doing the math showed me a pair of 56pf in series would give me a tighter tolerance. They weren't very expensive so I picked up twice as many as I need to replace them all. Then I'll also use my meter to get as close to the final value 27pf as possible. Yah. Overkill. That's some of my OCD showing.
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
The actual value is likely to not be all that important, as 27pF is very minimal to begin with.
If you buy old stock styrene caps, take some steel wool and clean the leads, as you'll need to solder these very quickly so they don't melt.
For small pF value caps, is it important the material they are made of?
Can you use a common disc ceramic cap or a mylar in its place?
Is polystyrene specific for frequency use? Or their high insulation makes them needed?
charles
Eh, yes and no. Based on the value of these caps, one would guess that they are suppression caps for very high frequency stuff. If I had the amp in question on my bench, I would probably put in a mica cap, as they are a little more tolerant to the heat that's generated right next to them.
Now, if you have some small caps in an EQ network or elsewhere where there is actual signal current passing through them, then the composition of the capacitor becomes much more audible and ceramic caps maybe should be avoided.
The nice thing about polystyrene capacitors is that they cost very little and sound incredibly good.
The caps in this case are in conjunction with pins on either side of each signal tube. So maybe this explains the use of polystyrene?
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
27pF just isn't big enough for audible frequencies under 99.9% of circumstances. These caps are likely for RF suppression, and their composition shouldn't be particularly audible.
Nt
Thought it was a mylar?
The manual for the MKII says the total value is 27pF 630 volt polystyrene.C5 C6
I'm not sure how you get 27pF from two series-ed caps?
Edit; Oops, wrong manual.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 06/07/15 06/07/15
What was I thinking - it is a classic polystyrene case.
Yes, it's clearly a polystyrene but without the proper schematic I don't know what value.It would be easy enough to measure the good one if I had it here.
Maybe the OP has a multimeter with a cap checker?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 06/07/15
It is 27pf on my schematic and manual also. But they ended up using a pair of 56pf in series to arrive at the value. At least if I did my calculations right. 1/c = 1/56 + 1/56. Heaven knows how someone came up with the formula but my meter measures the pair almost dead on where it should be. I got the formula off the net. So I ordered several pairs. Thanks for helping with this thread.
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Submit it to them and maybe you can get an answer?
Ended up ordering them from justradios.com. First time I heard about them. Up here in Canada so convenient for me. Not the prettiest website but lots of cool content. Funny never came across them before. Thanks again for your help!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
I think that is a capacitor?If you don't have a schematic they you will need a DVM that can read capacitance. I'm sure it's a very small value you can read from one of the others.
Edits: 06/06/15
By golly, you're right. I missed the boat on that one. Thought they looked familiar, but I only knew them as larger by-pass caps.
Thanks all for prompt reply!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
its a polystyrene capacitor
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