This set is about as close as we can get in Oz to a pre-war TV in the UK!
It would have been around for the start of TV in Australia and almost certainly would have shown the 1956 Olympic games.
I haven't even taken the back off it yet but my friend who sold it to me assures me its original AWV 17HP4B CRT is good.
He did say the IF gain is very low and that will need attention.
This is the only TV I've ever come across that's fitted with a number of UK-made Ediswan valves. Set makers here in the 50's and 60's would have been desperate to have to import valves because of the import duty on them.
The tuner is fitted with a 30L1 in the RF socket and a 30C1 in the mixer/osc. The IF is populated with 6F12s.
Are any of these still available in the UK?
Actually I'm not too worried because the pinout of the RF amp is virtually the same as a 6CW7 (ECC84?) and the 30C1 seems to be pin for pin for a 6BL8 (ECF80).
The 6F12 seems to be very similar to a 6BZ6 or a 6CB6 (EF??) except G2 and G3 are reversed.
A pretty TV this ain't! But it has history.
@irob2345 It has a very HMV look about it. The 6F12 is equivalent to the EF91 which was a very common valve in the UK. It has lots of other ID numbers depending on who made it including some military CVxx numbers. The Mullard ones have a nice blue coating on the inside of the glass to prevent the glass being bombarded and releasing gas as the anode didn't extend all the way around so a few Electrons slipped through!
Someone like Langrex will have those valves, but most likely badged as Mazda rather than Ediswan - Ediswan being the 'export' brand.
Seems an EF91 is a 6AM6. Thanks for the tip!
https://www.tubedepot.com/products/6am6-ef91
"It has a very HMV look about it."
Funny, right at the end of the B&W TV era HMV had a model sharing connection with Healing.
Here is the HMV of the same vintage:
![Finished job]](https://www.radios-tv.co.uk/wp-content/uploads/wpforo/attachments/1200/17250-Finishedjob.jpg "Finished job]")
@irob2345 Langrex in the UK have over 25,000 EF91s in stock but amazingly, not a single 6F12. I think 6AM6 was the designation used by Cossor.
Thanks for the Langrex reference.
I checked their price for EF91 but Tube Depot in the US works out less than half price for me.
I'll check my stock of 6BZ6 and 6CB6 first though. If I have them I may swap the 2 pins in the chassis and use them, as subsequent model Healing TVs in Oz did.
Should work better. The 6BZ6 has a remote cut-off characteristic so is ideal for AGC controlled stages. The 6CB6 is a sharp cut-off valve for following stages and has more gain than the 6AM6.
I actually got onto this TV over the last week and a bit.
It's nearly finished, I'll put up some pics.
After being cleared on the dim bulb it came up with a raster but no video or sound.
CRT is very strong for what is actually an RCA 17HP4B, complete with signature peeling dag!
Deja vu on the video, fault was a bad 6AL5 double diode in the video detector - completely dead. I replaced it with a couple of 1N4148s and got a picture. This would have to be the first time I've ever had to replace a 6AL5.
A few more fixes and replacement of a dozen 70 year old Ducon and UCC waxies, a couple of electros and some way-out resistors got a big improvement.
Looks like the Mazda IF valves have been replaced by much newer 6AM6s.
OK, now for the sound.
Plenty of signal into the ratio detector, nothing coming out.
Oh no, not another 6AL5? Yes, it was! Two bad 6AL5s in one TV! Probably why the last guy gave up on it! I bet he swapped them, with, of course, no result!
A shot of my workshop from the kitchen, the Healing is the TV top left, overpowering the camera.
Finally all finished, CRT re-dagged, rotted yoke plastics replaced, 70 year old UCC filter cans replaced with NOS Elnas, DC coupled video mod carried out.
Not too shabby for a 70 year old tele!
It's not quite perfect though. Note the horizontal non-linearity - slight squash of the RHS of the raster. This TV has no horizontal linearity coil so that's to be expected.
But what would you expect from what is a very basic TV design?
Despite the simple AGC, the black level tracks well (now with the DC coupled mod), probably a result of the AGC augmentation from the sync separator - a clever technique I've seen on a few other designs of this period.
Nice work on the Healing, it has come up pretty dam good and looks like the CRT is in good health going by those pictures. Our native NZ black & whites don't go back that far but we did have some sets made around 1959/1960. I see you've those Philips mustard caps under the chassis - I swear by those when doing up old TVs and radios.
All those mustards were already there when I got it.
After I put the back on, another two faults developed (as they ALWAYS do).
First was an intermittent volume control. That turned out to be a bad loudness tap on the pot. I removed the connected C and R to ground and that fixed it.
Next was a very occasional top linearity wriggle. Just like you were wiggling the pot up and down.
With unjustified confidence I replaced the 820 ohm carbon comp resistor in series with the pot that measured 980 ohms. Made not a scrap of difference!
Must be the pot then? Replaced it with a new one - nup, fault still there.
OK, what about the other 3 resistors in the feedback network? They all measured more than 20% high.
No, not that either! (I normally avoid shotgunning for that reason!)
Only thing left was the valve, a 12BH7. The one in there was a Russian "Electro-Harminex". I didn't have a replacement (or so I thought.) So I plugged in a 12AU7. A tweak of the lin pot and Perfection was the result.
Not happy about running the poor little 12AU7 in this circuit for any length of time, I had a scrounge through a box of chassis pulls someone gave me years ago. And came up with an Oz AWV made 12BH7 (branded "Miniwatt") that looked like it had done very little work.
And that seems to be it. Many hours running, no more top of raster wriggles.
It's not the first time I've had issues with Audiophool Russian valves in TVs! Russian 6BM8s (ECL82) just don't have the necessary grunt to work properly in most TV vertical sockets.
Ah right, well that would've made the set a bit easier to work with not having to change those caps out. Yes its always the way, I'm sure the sets lie in wait and then spring the new niggly faults when the back goes on. If I'm using a particular set at one time, I always run it with the back off for this very reason! Good find on the vertical fault. Yes I've also has some problems with those Russian valves in audio as well. Nothing like a genuine valve that you know is just going to work! The majority of the sets I've got have either ECL/PCL85's as vertical outputs and ECL82's in the audio section.
Yes Glen that dates your TVs to mid '60s.
The more screws there are holding the back on, the more likely it is to play up when you screw it back together! It's still good tonight, should I put the back on again?!
@irob2345 Yes, most of my black and white sets are from the 1960's. Did you get daring and put all the screws in the back? If so is the set still behaving? 😀
Not yet. This morning, during the first minute of run time, the test pattern shifted about 2mm sideways both ways a few times in the usual intermittent manner!
It hasn't done it since...
Am I expecting too much from a 70 year old tele? A fellow old TV collector maintains that such behaviour is part of their charm!
@irob2345 It could be the horizontal hold control or something else settling down. For a 70 year old set definitely not! That fact it has survived this long and is operational again is a testament. Agree the odd quirks are part of the charm indeed!
Yeah, running now. It hasn't happened since.
Update:
Back and base are screwed on. New anti-scratch feet fitted.
It's been some weeks now and it hasn't exhibited a single blemish!
So I think this one is done.
