UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Philips210 · 31st Jul 2018, 11:47 pm

Well done for your perserverance FiveBobRepairs! The R707 is horrible to work on, not as bad as a R700 though, but worth repairing all the same. They are not really in the same league as Hacker sets for build quality and serviceability.
Regarding the R707 IF module, I use some short, temporary, jumper wires to test the module away from the the main board. This saves the wasted effort of refitting an untested IF unit. The same idea also applies to the Mullard IF unit used in the Roberts R600.
As you probably know, the tin whisker problem is not only confined to the AF11x transistors but also applies to the germanium audio output transistors such as AC128, AC188 etc. I had such a problem with the AC188 in my last R707 that I repaired. It had a low reading between emitter and the case of the transistor. The normal junctions were otherwise OK.

Regards
Symon.

31st Jul 2018, 11:47 pm	#10
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,579	Re: Roberts R707 Well done for your perserverance FiveBobRepairs! The R707 is horrible to work on, not as bad as a R700 though, but worth repairing all the same. They are not really in the same league as Hacker sets for build quality and serviceability. Regarding the R707 IF module, I use some short, temporary, jumper wires to test the module away from the the main board. This saves the wasted effort of refitting an untested IF unit. The same idea also applies to the Mullard IF unit used in the Roberts R600. As you probably know, the tin whisker problem is not only confined to the AF11x transistors but also applies to the germanium audio output transistors such as AC128, AC188 etc. I had such a problem with the AC188 in my last R707 that I repaired. It had a low reading between emitter and the case of the transistor. The normal junctions were otherwise OK. Regards Symon.