I'm currently doing another HMV F series, this time an F4. After a 2 day electro re-form and a complete paper re-cap, it ran at first switch-on. Another bad mica in the hor. drive cct., there were styros in the other places where you normally see micas in this chassis. Someone a long time ago modified the hor osc. reactance stage to the F5 circuit, I'll leave that in.

This set looks like it has done a lot of work but it still has its original 60 year old 6R3 damper! Complete with EMI's white markings so it's definitely a factory fit..

6R3s and 6AL3s must be the most commonly replaced bottles in the history of TV, but this one is a survivor. Still with as-new emission and the getter looking as shiny as the day it was made. It's an Aussie Mullard.

Now, I started repairing TVs as a kid in the 60s and it was rare to see a 6R3 still working back then. Anyone else ever seen a good one this old?

On the subject of longevity, this chassis was quite badly nicotine stained, but it must have had a coating of dust underneath because WD40 and paper towels cleaned it all off quite easily, leaving a pristine zinc plating that looks as bright as the day it was made. Protected by the dust and a known carcinogen?

Were I worked in the late 60s, an F series came in from a pub in Balmain so coated in nicotine that it was barely recognisable. It was truly foul and no-one would touch it! The workshop manager, a hitheto heavy smoker, kicked the habit that very day! Saved his life I reckon.

I am glad all the nicotine came off the chassis. The dust underneath protected it.!!!
There is an equal amount on the cabinet but it should clean up okay.

Amazing about the 6R3's given that it has done a lot of work.
These old TV's certainly provide some surprises don't they.

I used to do in house TV repairs in the mid 70's as and found the worst offenders to be oil heaters.
They left a slimy deposit on everything.

Some people were still using B&W sets from the late fifties/early sixties which had a separate safety glass.

Some of these had so much deposit on the tube face and safety glass it was hardly watchable.

When I removed the safety glass (particularly difficult on AWA sets) and cleaned things up the customer thought you'd performed a minor miracle!

With regard to 6R3/6AL3s I think the originals were of much better quality than the later replacements. Particularly Trigon branded ones which fairly often went up in a shower of internal sparks from new.

What was the difference between the 6R3 and 6AL3 and why did so many 6AL3's go to air because I lost count how many times I'd find a failed 6AL3 in a TV when I used to repair them in my younger days back in the 1980's?

Good question Daro.

I cannot remember ever seeing a 6R6--wouldn't know what one looks like, but I can say one thing about 6AL3's----- every one I came across
that needed replacing lost vacuum rapidly. Always milky, and often fractured envelope around the top cap.

Why? Too much heat stress, and/or mechanical stress from too short anode lead? Underrated valve for the task?? Any clues anybody?

Yes you are right about the 6AL3.

The 6R3 was its predecessor. Because the heater-cathode withstand voltage needs to be several kV the 6R3 has a ceramic tube inside the cathode, with the heater inside that. It made the warmup time longer, so the 6AL3 was developed to address that issue. A very high power heater was used.

6AL3s seemed to fail mostly in wet weather for some reason. Glass cracked, tell-tale white getter. In the service van stock we'd keep at least a dozen 6AL3s, sometimes even that wouldn't get you through the day!

Eventually Japanese Hitachi 6AL3s came along and solved the problem.

Although I never repaired TVs, I seem to recall the 6R3 being slightly shorter than the 6AL3, but otherwise they looked much the same. I might be wrong though ... it's been a long time.

Yes Rob you are right.

The long warmup time of the 6R3 was probably the main reason it was superseded. I timed the F4 this morning and the picture takes a full 29 seconds to appear after the sound. That must have been off-putting for many customers, a degree of impatience and knob twiddling would have happened.

The 6R3 data sheet does warn about this.....

That’s probably the reason they lasted so long.
Slow warmup means slow glass expansion.
And we know that 6AL3 failure was usually(always) gassed(broken).
JJ

Looking at the specs 6R3 has a lesser rating, but like several TV valves & several Vertical OP valves it came down to quality & some were quite unstable. I think 6GV8 was mentioned at a radio club meeting as one offender. An interesting note in the Philips book re 6AL3 is that the heater should be negative relative to cathode.

I would not be surprised at ruggedising a valve. HP did that to I think 6BE6 to use it in computers and Sovtek changed the construction of 5Y3 to more like that of 6V* rectifier series. Its got a huge filament, & by the way it behaves, a cathode sleeve.

Construction in 6X5 was also an issue. Despite being designed as a car radio rectifier, early versions had a notorious habit of getting heater cathode shorts. I have seen quite a few references to some used in Zenith radios in the US, being very marginal & taking out transformers wholesale.

Hi Marc, the 6X5, remember it was quite common to see the heater unwinding out of the top of the cathode sleeve and going for a wander inside the valve?
Fred.

Totally concur: Seen a few of those & they did not all fail. Again designed flawed and this found this out very quickly in service. The over & under ones were the the ones I consider a fail. Because they had no effective support top & middle, I am quite sure that this contributed to them sagging, or bending sufficiently for the cathode sleeve to short to the heater.

That was a sort of similar thing to RCA style 5Y3 where there was only one position to run it sideways. Basically the filament strip would sag & it got worse with age. This filament was in what was like an air-conditioning duct, and hung like washing from a line. If you turned the valve sideways without thinking, most times it would hit the plate, with spectacular results.

You can pick radio's that were in kitchens as these normally have a liberal amount of fat deposited within & that acted as a binder for grot.

the 6X5, remember it was quite common to see the heater unwinding out of the top of the cathode sleeve

Yes, but I've seen it happen more often on the 6X4.