Transistor Replacement - Page 3

poobah · 14th December 2005, 03:33 AM

Hey Portland,

Would this be a mid sixties vintage?

I remember seeing those in Heathkit radios...

anatech · 14th December 2005, 12:50 PM

Hi Portland,
They are either 47 pF or 470 pF. I am leaning toward 47 pF myself. Can you measure one? Really doesn't matter. We are just curious.

-Chris

portlandlay · 14th December 2005, 02:36 PM

I took one out yesterday to give my multimeter a stab and of course it only has resolution down to 1nF.

However, I measures it and it says 1 nF. I measured a cap that I had laying around that is .0047uF and it reads 5 nF. So it looks like it is working. My guess is that it is actually 470pF for it to read 1nF. If it were 47pF I doubt it would register a value.

I will measure more of the caps as I have decided to do the entire board with new components while I have it apart.

Poobah, this is a 1972 Sugden amp from the UK. They started making these in the late sixties and I bet stocked up on supplies to last the few thousand produced so I am sure the caps date back to the 1960's.

What type of cap should I use to replace these? I found some wima films this size but they are rated at 1600v and since this might see 36v they are not really appropriate.

I have one more mystery (to me) component that I will take a picture of. It is a clear plastic looking deal that looks like it is either a cap or a diode of sorts.

I hope that when this is all said and down the amp works

poobah · 14th December 2005, 03:44 PM

For safety's sake, your caps should have the same (or greater) voltage rating as your power supply rails... This is because you never really know how things are going to "power up/down". Plus, if get a failed component; you don't want a chain reaction of failures... though sometimes there is nothing you can do.

Teflon are supposedly the best... but who has the money? If there really IS (no opinion, or facts... yet) a difference; it is small.

Polypropylene is good... "foil" instead of "metalized" is thought to be better. They are physically larger though.

I don't know what you have access to but Sprague Orange Drops (715's 716's) are good and very friendly to the wallet. These are FILM/FOIL/Polypropylene. Measure and read the specs to make sure they will fit?

Your caps are probably MYLAR (polyester... popular in that era)... they may sound fine just the way they are.

poobah · 14th December 2005, 04:25 PM

Sorry Portland,

I gave you a bum steer Sprague 715P's don't go that small... missed it by THAT much.

See if works first... if not I'll find you something but will need to know the hole to hole distance.

That ole' cap is probably fine though.

AndrewT · 14th December 2005, 04:36 PM

Hi,
the clear components may be polystyrene caps.

anatech · 14th December 2005, 07:46 PM

Hi portlandlay ,
Until you can verify the value, leave them in. If they are silver mica, keep them.

-Chris

14th December 2005, 04:36 PM	#26
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, the clear components may be polystyrene caps. __________________ regards Andrew T.

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14th December 2005, 03:33 AM	#21
poobah diyAudio Member Join Date: Nov 2005	Hey Portland, Would this be a mid sixties vintage? I remember seeing those in Heathkit radios...

14th December 2005, 12:50 PM	#22
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Portland, They are either 47 pF or 470 pF. I am leaning toward 47 pF myself. Can you measure one? Really doesn't matter. We are just curious. -Chris

14th December 2005, 02:36 PM	#23
portlandlay diyAudio Member Join Date: Dec 2004 Location: Washington State	I took one out yesterday to give my multimeter a stab and of course it only has resolution down to 1nF. However, I measures it and it says 1 nF. I measured a cap that I had laying around that is .0047uF and it reads 5 nF. So it looks like it is working. My guess is that it is actually 470pF for it to read 1nF. If it were 47pF I doubt it would register a value. I will measure more of the caps as I have decided to do the entire board with new components while I have it apart. Poobah, this is a 1972 Sugden amp from the UK. They started making these in the late sixties and I bet stocked up on supplies to last the few thousand produced so I am sure the caps date back to the 1960's. What type of cap should I use to replace these? I found some wima films this size but they are rated at 1600v and since this might see 36v they are not really appropriate. I have one more mystery (to me) component that I will take a picture of. It is a clear plastic looking deal that looks like it is either a cap or a diode of sorts. I hope that when this is all said and down the amp works

14th December 2005, 03:44 PM	#24
poobah diyAudio Member Join Date: Nov 2005	For safety's sake, your caps should have the same (or greater) voltage rating as your power supply rails... This is because you never really know how things are going to "power up/down". Plus, if get a failed component; you don't want a chain reaction of failures... though sometimes there is nothing you can do. Teflon are supposedly the best... but who has the money? If there really IS (no opinion, or facts... yet) a difference; it is small. Polypropylene is good... "foil" instead of "metalized" is thought to be better. They are physically larger though. I don't know what you have access to but Sprague Orange Drops (715's 716's) are good and very friendly to the wallet. These are FILM/FOIL/Polypropylene. Measure and read the specs to make sure they will fit? Your caps are probably MYLAR (polyester... popular in that era)... they may sound fine just the way they are.

14th December 2005, 04:25 PM	#25
poobah diyAudio Member Join Date: Nov 2005	Sorry Portland, I gave you a bum steer Sprague 715P's don't go that small... missed it by THAT much. See if works first... if not I'll find you something but will need to know the hole to hole distance. That ole' cap is probably fine though.

14th December 2005, 07:46 PM	#27
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi portlandlay , Until you can verify the value, leave them in. If they are silver mica, keep them. -Chris

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