Hi all , Iam currently working on a HMV 61-51 Radio. The problem I have is, it will run beautifully for about four minutes, and then cut off. I have checked all resistors and changed some of the caps. Hope someone can help. bowler

At least we know the length of a piece of string.

Had one of those this month in the form of a Peter Pan. It had already fused several resistors around the 6A8 so the valve tester just confirmed what I already knew. That also had a similar issue to yours that sent a 6V6 to the bin.

Fault finding in a set with old electrolytics and wax paper caps in it is time wasting.

Some of that series had two 22K resistors in parallel feeding the RF /IF screens. Been counters saw them replaced by one 10K and current squared by resistance, saw them cook by overload. need to be 2W.

That fault can be debris, a thermal fault, Shorting; dry joint, dud tube, a resistor cooking; Bad / under rated electrolytic, or a tube.

Start as I do after repairs by using something like IC clips on a voltmeter to monitor "B" volts. Normally when they die from other than a short the volts go up. That could be a Mica cap failing albeit they usually fail noisy.

Marc

Firstly I would divide your problem by half.
When it's failed have you lost the audio section or the RF/detector section.
An easy check. Checking individual components at this stage would be a waste of time.
Check also a few basic voltages, eg 6M5 anode voltage, etc.
Then when we have more info, it can be narrowed down to component level.
Also have you wriggled the valves/sockets whilst the radio is running?
Even a slight technical tap on the chassis with the handle of a screwdriver?
More info needed.
JJ

Hi thanks for your replies. There was a static sound when I bumped the 6Be6, I replaced the valve socket and now all is well. bowler

Some sockets get silver migration off the tube others can spring open a bit & break internally. Often get that.

I just use a spike to close them up and a Gas Welding nozzle file to clear corrosion.

It normally pays to take the tubes in and out, a few times to scrape the pins & socket.

To get Silver Migration off the tube. A dip in nasty Acid like HCl works well: Wash the tube well. Also cleans the pins.

Marc