Murphy V180 restoration.

[DangerMan]

You've got it David, that's exactly what I was thinking, everything bracing everything else.

Pete

[Heatercathodeshort]

This picture may help David. I must say that the cabinet is very strong. Maybe yours has been eaten away a bit. J.

[FERNSEH]

The department of adaptor plates and brackets has come up with these beauties. The brackets will locate the chassis in the cabinet and stiffen things up a bit. Let's find out if they fit.

DFWB.

[FERNSEH]

The brackets are now in place. These certainly stiffen things up. The cabinet is no longer flexible and the chassis is centralised.
The next stage is to dismantle all the metalwork prior to repainting in a dark grey colour.

DFWB.

[Heatercathodeshort]

A lot of work there David. If you need any detailed pictures, let me know. I think the electrical side will be a lot easier than might be thought. John.

[Tazman1966]

Another labour of love David! Well done

[FERNSEH]

Well here goes. I've fitted a new mains lead, replaced the fuses and checked the on-off switch contact resistances.
Standard HKS test procedure, "just plug it in" and the big news is the all the valve heaters are lit up.
Next stage is the brave bit, to plug in the UU8 HT rectifier.
Standby for more news.

DFWB.

[Heatercathodeshort]

Do you want me to come up and hold yer hand David?
That UU8 can be a nasty rectifier but most of the used ones seem to be OK. It's the new ones that seem to like to behave like fireworks. I can send you my pair of rubber gauntlets if your scared..
Just stick a meter across the H.T. line and check that line output screen decoupler, then 'plug it in'!
At least the valves light up. Regards, John.
PS This little cutie looks kinda pretty don't you think? Your example with the metal skirt must be a very early version.

[Heatercathodeshort]

The 1960/61 edition of the Ediswan valve data book gives the details of the beastie. The nearest Mullard valve is the GZ32 but that has a 5V heater and an International Octal base. The metal jacket appears to have been stripped off around 1951. J.

[FERNSEH]

Hi John,
Still no HT supplied to the set but that's not on account of lack of braveness but due the fact the line hold control has fallen to bits and a number of wires have become detached from various parts of the chassis.
The truth is I'm attempting to restore this set in my garden workshop and there are at present not enough facilities in there to do the full restoration job. So for that reason I'm going to finish the job in the Shop's workshop.

DFWB.

[Heatercathodeshort]

Sounds like you have had some garden gnomes doing a bit of sabotage. John

[Ed_Dinning]

Hi David, big incentive to get the wiring completed before it gets really dark!!!

Ed

[FERNSEH]

Hi Ed,
Those halogen ceiling lights installed in the garden workshop are energy wasteful and should be replaced with conventional fluorescent tubes.

The faulty line hold control has been replaced and those loose wires have been traced to the correct connecting points, thanks to the excellent Murphy V180C service manual. Thanks to Lloyd the restoration job is speeded up.

DFWB.

[Heatercathodeshort]

Remember David, you will need a neck on that CRM121 if you want to get a picture..J.

[FERNSEH]

Originally Posted by Heatercathodeshort

Remember David, you will need a neck on that CRM121 if you want to get a picture..J.

Hi John, Does it need one?
Today's news is that the chassis and the spare CRT are now in the proper workshop so it's time to get down some real TV servicing.

Check out that UU8! It's metalising is bit flaky.

DFWB.

[Heatercathodeshort]

Looks like it has been out in the sun too long David but I bet it is OK. Like everything in life, the flashy new things don't stand up to punishment. John.
[PS. I have a neck for your old tube if you fancy gluing it back on. Just a kind offer.

[FERNSEH]

Before the set is plugged into the mains it's a better practise to check the resistance across the HT line to to chassis. The figure for this set is only 18,000 ohms, that might be a bit low, I'd thought about 40 to 50 Kohms would be a better figure.
So, before the mains is connected up it's a good idea is to give all those capacitors taste of electricity. To do this a 1N4007 diode and for starters a 150Kohm resistor in series supply the HT line. The voltage is monitored and when the meter reading levels out the resistor is reduced in value until the correct HT voltage is achieved.

Let's see what happens.

DFWB.

[Heatercathodeshort]

Oh no! David, this sounds like you're torturing the poor thing! If your going to give it a 'taster' then it's only fair to give it the full blown meal.
I have an old brass diving helmet you can borrow if you feel you need some protection from flying UU8 debris.
I have measured my H.T. line to earth from the 500m/s HT fuse. 19K so it looks very similar to yours.
I set a very bad example. UU8's are getting a bit scarce so maybe your caution is justified and your example has been very badly stored. I think maybe the lamp limiter should be roused from its slumbers. John.

[FERNSEH]

The series resistor was progressively reduced in value until the HT voltage rose to the correct figure for this receiver, 280 volts.
No hisses or bangs. It's time to "grasp the nettles" and insert the UU8 valve and plug the set into the mains. The result of all this bravery, nothing! That UU8 might not look pretty and turns out it's pretty useless as well.
So another UU8 goes in and this time success. The HT voltage rose to 300 and quickly fell back to 280V after the U282 boost diode warmed up.
And it get's better, a tiny spark can be drawn from the anode of the 6P28 line output valve and an even bigger spark is present at the anode of the U24 EHT rectifier. No measured DC EHT voltage though. I disconnected the Visconol EHT smoother but no improvement. The U24 might be faulty although the heater checks OK.
Then, disaster! The U282 reclaim diode started to flash over internally and in due course a purple glow became apparent.
The Mazda U282 and the U281 are the first diode valves made by Mazda to function as TV timebase energy reclaim diodes. I'll replace the faulty valve with the much better Mazda U301. The valveholder has to be rewired in order to use the later type of valve. The U301 has a top cap cathode connection.

Nevertheless, as long as the line transformer holds up I reckon it'll not be too long before this set is displaying pictures.

DFWB.

[FERNSEH]

I made good progress on Sunday evening. A new Mazda U301 replaces the faulty U281 reclaim diode. The base connections of the two valves differ. On the U281 the heater pins are 2 and 7. On the U301 the heater pins are 7 and 8. The anode is pin 5 on both valves. On the U281 the cathode is pin 7. On the U301 the cathode connection is the top cap.
It was a simple task to rewire the valve base. The cathode of the U281 is connected to chassis. The cathode wire was cut off and the heater lead to pin 2 was transferred to pin 7. For the U301 a top cap connector was found and it now connects to a convenient earth point.
Time to test the set. A spark was present at the anode of the U24 EHT rectifier, still no DC output. A replacement U24 was plugged in and now 4KV is indicated on the EHT meter, that's too low. The line output valve in this set is a Mazda 6P28, I've replaced it with a Mullard EL38. Now that's more like it, almost 6.5KV is available.
The line oscillator is running slightly fast at 95 microseconds, it should be more than 100 microseconds for 405 line TV. Several 6K25 thyratrons were tried with no improvement. The sawtooth drive to the control grid of the line output valve is >75 volts peak to peak.

The original U24 EHT rectifier valve was tried again and more than 6KV is still available using this valve. It's likely this valve is down on emission as a result of the leaky Visconol EHT reservoir capacitor.
Tomorrow I will wire up a new Mazda octal socket for the replacement CRT.
There could be chance of some sort of display on the tube screen.

DFWB.