UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Pye 1004 (Transistor Black Box) amp faults, help wanted please

Nickthedentist · 18th Sep 2019, 9:03 am

Sorry about the slow progress. The new output pair has arrived, but I haven't fitted them yet.

I've removed the preceding 5 transistors and tested them on my Peak analyser. All are identified as Ge transistors with sensible and similar test results, except for the only NPN transistor, VT4, which in my example is an NKT733. This gives an HFE (?) reading of 1, whereas all the PNP examples are well into double figures.

Should I worry about fitting the output pair because of this? Or Is this normal? Or should I source a NOS NKT733 at some expense?

Snippet of circuit diagram attached.

Cheers,

Nick.

18th Sep 2019, 9:03 am	#16
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,846	Re: Pye 1004 (Transistor Black Box) amp faults, help wanted please Sorry about the slow progress. The new output pair has arrived, but I haven't fitted them yet. I've removed the preceding 5 transistors and tested them on my Peak analyser. All are identified as Ge transistors with sensible and similar test results, except for the only NPN transistor, VT4, which in my example is an NKT733. This gives an HFE (?) reading of 1, whereas all the PNP examples are well into double figures. Should I worry about fitting the output pair because of this? Or Is this normal? Or should I source a NOS NKT733 at some expense? Snippet of circuit diagram attached. Cheers, Nick. Attached Thumbnails