Bush Vtr 103 noise

[tim.54]

After labouring on a couple of Bush valve radios i`ve acquired a Vtr 103
its reasonably tidy and in working order . when i switch it on theres fairly audible noise (hash ? for want of a better word) not too distracting when tuned to a station but always there , doesent alter with volume it stays constant , just wondering if this is normal never having owned one ? also Fm performance isn`t stellar, lot quieter than am plus some distortion any pointers ? it still has the dreaded afx transistors but it is working in a fashion . its a good looking set so would like to get it up and running to its full potential . all advice appreciated ,
regards, tim.

[Refugee]

Those red-yellow-black capacitors have a nasty habit of going open circuit.

[ed731pdh]

Any of those blasted AF transistors in there. I notice from the circuit diag that some of the transistors have a shield leg, which implies AF115s etc. and the dendritic growth that goes with them.

[Nick]

Might be useful reference: Bush VTR103 repair

[Raditechman]

I repaired one of these Bush radios for a friend last week. It did not work apart from the AF stages. I replaced the three IF stage AF116's with BC214's which restored the LW and MW. Replaced the AF114 and AF115 in the VHF tuner with AF125's that restored the VHF FM. There were a few Hunts capacitors which were leaky so I also changed them, plus one electrolytic.
The set works very well, although the volume control is a little scratchy, I will fit a replacement if they want it, later on.
I have the original Bush manual for this set if you want a PDF scan of it let me know.
John

[ed731pdh]

I was always of the impression that the early AFs used to just suffer from dendritic growth. Turns out now that they can also become noisy in operation and if you have a noisy transistor in the RF stage the noise is amp'd all the way through the radio. I would seriously consider changing out the AFs one at a time until the hash disappears.

[Mark Hennessy]

If the noise is present at all settings of the volume control, then surely that implies that the audio stages are the problem?

Sure, the AF11x transistors grow tin whiskers, and might be responsible for the weak FM, but tackle one problem at a time...

My experience is that OCxx audio transistors are pretty reliable, but do check them by substitution if possible. Then, suspect any carbon composition resistors that are reasonably early on in the signal chain. Of course, it helps to have access to another example of the set, so that you can compare the noise levels...

If the FM performance is still weak after "treating" the AF11x transistors, you might need to try a line-up. If that fails to improve things, it might just be that the set is working as well as it ever did. Early FM sets were often a lot less sensitive than modern ones - especially UK-made ones in my experience. Sadly, Bush didn't quote sensitivity levels in the service manual, so it's hard to be more specific in this particular case.