UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - PIN diode band switching yaesu ft-767

Steve G4WCS · 13th Feb 2021, 10:41 pm

Evening all, hope everyones not suffering too badly with the weather and cabin fever setting in.

Ive been doing some further investigation with the 767 receiver. Using the crystal marker as a signal generator, I have confirmed it is profoundly deaf between 0.5 and 1.5 Mhz.

Geoff at Castle Electronics had said that they can suffer from PIN diode problems on the RF unit, and if there is a leaky one on one of the filters it can leak signal on the other bands. Ive had a look at the rf unit diagram and one of the filter sections does cover 0.5-1.5, so Im suspecting this (however havent discounted a switching relay yet).
Unfortunately he has stopped servicing these, and the days of nipping over to see Harry Leeming are long since gone

Can anyone explain to me in simple terms how the PIN diode switching is implemented, how they can be checked (ie can they be checked in situ or do they need removing) or shall I just bulk replace them ?

They are an ISS83, is there a readily available equivalent ?

Thanks in advance

13th Feb 2021, 10:41 pm	#1
Steve G4WCS Heptode Join Date: Sep 2004 Location: Preston, Lancashire, UK. Posts: 632	PIN diode band switching yaesu ft-767 Evening all, hope everyones not suffering too badly with the weather and cabin fever setting in. Ive been doing some further investigation with the 767 receiver. Using the crystal marker as a signal generator, I have confirmed it is profoundly deaf between 0.5 and 1.5 Mhz. Geoff at Castle Electronics had said that they can suffer from PIN diode problems on the RF unit, and if there is a leaky one on one of the filters it can leak signal on the other bands. Ive had a look at the rf unit diagram and one of the filter sections does cover 0.5-1.5, so Im suspecting this (however havent discounted a switching relay yet). Unfortunately he has stopped servicing these, and the days of nipping over to see Harry Leeming are long since gone Can anyone explain to me in simple terms how the PIN diode switching is implemented, how they can be checked (ie can they be checked in situ or do they need removing) or shall I just bulk replace them ? They are an ISS83, is there a readily available equivalent ? Thanks in advance Attached Thumbnails