Bush VHF64

[boater sam]

You do as you wish Rob but I have never found it necessary and there has been numerous occasions when the "restorer" has messed up with introduced errors and wrong parts that have resulted in mammoth threads on forums and a failure to get it sorted. Eventually the guy throws in the towel and the set goes in the bin.

If it works now, there can't be much wrong with it. They were built with fair components, but not perhaps as good as modern ones, and they have worked for 60 odd years.  Valve radios of this vintage were not very critical, component values varied a lot, tolerances were large.

[Refugee]

I have had tubular ceramic capacitors fail. One took out a wave change switch.
The grey one was across the 6.3V heater supply and the one that took the switch out was on the HT in the FM front end.

[boater sam]

Thankfully, none of those in a Bush as far as I know. I never liked those tubular things, didn't the wires break off as well?

[Refugee]

It was a Phillips set. I don't think they were that much worse than anything else for broken wires.

[Terry]

Chassis looks good, all original Mullard valves?

Not directly applicable to the VHF64 but I came across a few NOS valves yesterday - all Mullard, even if one was in a (correctly marked) Mazda box!

Two of them were PCL85/805 but one looked rather odd. It was in Kradlepak, with the trademark, type number, etc. marking face upwards but there were two things I noticed: one was the font used for the type number looked wrong and there was a strange symbol:└┘ on it.

When I inspected it in more detail, the pentode anode was black, rather than the usual dark grey colour and there was no batch/date code etched into the glass. It was clearly marked, though, as made in Great Britain.

Obviously a buy-in but who was the original manufacturer? Another PCL85/805 was perfectly normal in all respects, including the Blackburn date code.

[boater sam]

A blackened anode may suggest military spec, helps cooling by radiation.

[Old Sparky]

I admit to usually changing all waxies and Hunts caps. in vintage radios, etc., including a VHF61 and a DAC10, both a few years ago. Neither was particularly easy to work on, the narrow, deep chassis in the 61 made components awkward to get at, whilst the preset button mechanism in the '10 didn't help accessibility, either, although most of the circuitry is on a tagstrip assembly, IIRC. That was the reason, ironically perhaps, why I did a full recap, and also changed some out of spec resistors on these two sets. Maybe having 40 years experience working on radios of all sorts helped, but I still proceeded with caution, and was rewarded with two good working radios afterwards.

[Murphyv310]

Sam's advice is spot on. I rarely replace the hunts caps on the heater supply nor the ones on IF amp cathodes, there's only a few volts there and even cracked they work fine.

[Murphyv310]

In valve sets back when I was a boy and before, you'd be surprised how far off resistors can be before there is any change in perceived performance.
See post 2 here: http://golbornevintageradio.co.uk/forum/...p?tid=6312&pid=68268#pid68268

[Geordie McBoyne]

I bought a VHF64 last year. In terms of sensitivity and selectivity I'm well pleased with it however the hum level is higher than what one would expect from this quality of receiver. The primary of the output transformer of the single EL84 output valve is supplied HT direct from the reservoir capacitor. This would be in order with a push-pull output stage because the ripple is cancelled out but not with a single valve output stage. Your comments about this would be welcome.
It's worth mentioning the Mullard 3-3 amplifier uses a similar HT smoothing arrangement.

Geordie McBoyne.