Trying to fix guitar amp Randall RH100 G2 head - power amp RG75B

[Will Puckett]

Allen,

I ordered mine off eBay from a Chinese concern. Also the small signal transistors which are somewhat critical to the bias circuit:

Here
2pairs(4pcs) 2SA1941 & 2SC5198 TOSHIBA Transistor A1941 & C5198 TO-3P https://r.ebay.com/qiX3si

5pair OR 10PCS Transistor TOSHIBA TO-220FP 2SA1837/2SC4793 A1837C4793 https://r.ebay.com/uzbmVs

50pcs 2N5551 Transistor NPN 160 Volts 600 mA TO-92 Package https://r.ebay.com/Mpu5in
50pcs 2N5401 PNP Transistor 150V 600 mA TO-92 Package NEW https://r.ebay.com/8QCzaY

Be very cautious about R47 and that 2N5551 with its head stuck in the heatsink (Q6)

 

[Alman]

Thanks for the reply. I am a little wary of ordering from ebay due to all the counterfeit parts out there.

Did you actually order from these sellers?

I have found from NTE some replacements that might work.
https://www.nteinc.com/specs/10to99/pdf/nte36.pdf For the A1941 & C5198 pair.
https://www.nteinc.com/specs/2600to2699/pdf/nte2647_48.pdf For the A1837 & C4793 pair.

I haven't found if anyone has used these as substitutes yet, but was considering ordering them from Newark along with the 2n5551 that has R47 attached to the emitter.
And yes the R47 is an issue too. The one in this amp was badly burned.

Do you think All the 2n5551 and 2n5401 should be replaced?
Also what was the value of R47? I have found one person that had a 220 ohm and soldered a 47 ohm in parallel with it which would bring it down to 38.7 ohm.

Allan