Wavetek 2407 Signal generator - UK Vintage Radio Repair and Restoration Discussion Forum

allan · 26th Dec 2019, 12:26 pm

My Wavetek 2407 signal generator is giving trouble.
My first problem was an MRF571 driver transistor went short circuit for which I found an exact replacement but then the output transistor went the same way.
I suspected tin whiskers so connected a PSU (reversed) across the emitter-base and removed the short which restored its operation.
I now think its happened again as the RF output goes off and on intermittently. Sometimes the RF goes off long enough for an error message to be displayed before going back on.
The device is an expensive MRF839F so I've ordered a similar shaped but cheap TP3034, but has anyone come across this sort of problem with early Motorola UHF transistors?
It seems these may suffer from similar trouble to the Mullard transistors used in Roberts radios.
Allan

MrBungle · 26th Dec 2019, 12:30 pm

Not seen it on those. I did have a couple of genuine MRF237s in a large batch that were DOA with shorts though but they are TO39 packaged. They were 1970s date coded. Can’t remember which end of the 70s.

26th Dec 2019, 12:26 pm	#1
allan Pentode Join Date: Oct 2005 Location: South coast near Ringwood/Christchurch, Dorset, UK. Posts: 230	Wavetek 2407 Signal generator My Wavetek 2407 signal generator is giving trouble. My first problem was an MRF571 driver transistor went short circuit for which I found an exact replacement but then the output transistor went the same way. I suspected tin whiskers so connected a PSU (reversed) across the emitter-base and removed the short which restored its operation. I now think its happened again as the RF output goes off and on intermittently. Sometimes the RF goes off long enough for an error message to be displayed before going back on. The device is an expensive MRF839F so I've ordered a similar shaped but cheap TP3034, but has anyone come across this sort of problem with early Motorola UHF transistors? It seems these may suffer from similar trouble to the Mullard transistors used in Roberts radios. Allan

26th Dec 2019, 12:30 pm	#2
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Wavetek 2407 Signal generator Not seen it on those. I did have a couple of genuine MRF237s in a large batch that were DOA with shorts though but they are TO39 packaged. They were 1970s date coded. Can’t remember which end of the 70s.