Transistor Replacement

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Transisitor Replacement

I am trying to bring my Sugden A21 (old) amp from the dead to the living.

It looks like one channel is dead and I think that a bad BFY53 transistor is the problem. The rest of the amp and the scematic only show BFY52. Since I am not a transistor guy I need help. I see that BFY52's are available and I want to use one of these instead. It looks like the h(FE) min for the BFY53 is 30 and 60 for the BFY52 otherwise they look very similar.

Is this OK?
 
Hey Portland,

If the schematic says BFY52 (high hfe) and you found a BFY53 (low hfe) on the board... especially if the other channel on the amp has a '52; the manufacturer may have been measuring 53's and sorting out and using the 52's with high gain... happens all the time.

Anatech is dead on the mark though... usually you can sub an otherwise equivalent transistor with another unit of higher hfe.

Hope this helps,
 
Thanks again.

I am going to order it today. I may as well change them all out since they are about $0.60.

Stephen


Perhaps you can help on another subject as well. There are a number of small passive components that look like they are caps but they read 470KAC and are light brown in color and look to have a wax center. The do not read 470k ohm with my meter. I can take a picture if needed.
 
Anatech,

Here is a picture of the part.

Thanks,

Stephen
 

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Chris,

I think that you may be right. looking at the schematic it looks like c10 may be one of these. That is 470pF like you said earlier. The AC must mean that it is a bi-polar elec. deal. Not sure what the K stands for or why the did not use a film type.

There is one more on the board that is not on the schematic but again they do differ a bit.

I can only measure capacitance with my multimeter and I will have to take it out of the circuit and even then it is iffy.

Stephen
 
After some searching on the web I am pretty sure that they are as you suspected caps. I think that they are either the 470pF or maybe 47pF.

The nomenclature looks like the 470 is 47x10^0 pF and the K means 10% tolerance. The AC I could not find but I am sure that this means that it is a non or bi-polar electrolytic. The problem is that the 10^0 may really be 10^1 so I will measure them all to see if I can get an average.

Thanks again. I can't wait to get this running.

After this I want to put together a JLH amp to cut my teeth.
 
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