TV22 Restoration
 

Hi Guys,

Well after days of trying and not really understanding TV circuitry at all I give up...

Can somebody please repair my Mk1 TV22. I have a TV63 in unrestored condition I would glady gve as payment or even good old beer vouchers.

I can supply some information on whats its doing if that helps and I am located in Birmingham.

Regards

Andi

PS Phone number by request

Re: Can somebody please repair My TV22
 

Hi Andi,

Why give up?

If I can get an old TV going then I am sure you can - remember, it worked when it was new!

Cheers
Sean

Re: Can somebody please repair My TV22
 

Hi Jarl, Lets have a description of symptoms and we may be able to give you some ideas.

Ed

Re: Can somebody please repair My TV22
 

Hi Guys, Hi Sean thanks for the moral support.

OK Most of the waxies have been changed. The 5 or 6 electrolytics have been reformed. All valves tested for shorts and conductance.

Low A1 Voltage at around 100v, replaced metrosil (didnt know how to test it) with the Resistor/Diode adaptation from Andys site.

No HT at all

Untested tube

But we do have all of the heaters including the DY51 which has its own heater winding on the LOPT so I know the primary must be ok

Thats about it to start.

Re: Can somebody please repair My TV22
 

Um....maybe I'm misunderstanding your symptoms but if I understand from the comment above that you have all heaters alight including the DY51 then you must have HT and the line must be running otherwise the DY51 would not be alight. It would of course be possible to have no HT with all heaters alight but the DY51 would not be alight. With no HT, you would have no boost. You could have low boost with normal HT or possibly low boost with low HT but it would be extremely unlikely that the DY51 would be alight.

Can you clarify please??? .


Rich

Re: Can somebody please repair My TV22
 

Hi Andi,

you must have some HT, otherwise the line output stage wouldn't run (no heater glow from the EY51). I would suggest measuring the voltage at the cathode of the rectifier (PY33?), and then working in from there. The rectifiers in these sets (TV22 / TV23) have too much capacitance in the filter, and you will often find the rectifier half low emmission, while the boost side tests as new - in this case, you can temporarily use a silicon rectifier.

Another useful tip on this range, for test purposes, you can disconnect the HT at the plug which connects the two chassis (leave all the other wires in), this will allow you to isolate any leaky wax caps.

Let us know how you get on.

Jim.

Re: Can somebody please repair My TV22
 

OK Will have a play with this again toorrow night, I did have heaters on the EY51 till I swapped out the Metrosil so I will put it back in.

Re: Can somebody please repair My TV22
 

Hi Andi,

The diode trick is a quick and dirty way of getting an A1 supply, but may well be loading the circuit too hard - if the metrosil is producing a voltage then it is probably working.

My first order of business on the sets I have done (5 now) is to get a line whistle - even if it is croaky and weak it does prove that volts are where they should be.

I really do not subscribe to the wholesale replacement of caps untill I have seen the item showing signs of life - HV caps are expensive to throw away on a set until you are sure that you are replacing the right parts.

As others have said, if the EY51 heater is glowing then the lopti is doing something.

Cheers
Sean

Re: Can somebody please repair My TV22
 

HT whistle I had plenty of, but low A1 grid volts regardless of Metrosil or diode/resistor substitution...

Thanks for the help so far guys, gonna have a few hours on it when I get home...

Andi

Re: Can somebody please repair My TV22
 

Hi, do you have 400VppH at the lopt end of the metrosil?

Kind regards,
Darius

Re: Can somebody please repair My TV22
 

Hi All,

Jim, I disconnected the HT to the IF Stage and up came a Raster for about 15 seconds...

Darius, The voltage into the Metrosil is only 221v DC measured on my Fluke DMM. Thats after the raster dissapeared as I wasnt watching the screen to start with. I was watching the heaters then glanced at the front and almost had a shock thta the tube and lopt appeared to be good (YAY!)

OK where next?

Andi

Re: Can somebody please repair My TV22
 

Ok, looks like low HT to me, certainly you have some issues in the RF stage . Dump the fluke DMM, connect your AVO (you do have one don't you;) ) to the HT line with the set turned off.

Apply power, and watch the HT rise - it should come right up to the corerect level far in advance of the rest of the set, then I would suspect it will drop off, as the rest of the circuit draws power.

If the HT is low in these early stages trace where the AC derived from - does it pass through any resistors?, if not you should have 220vish AC on the anodes of the rectifier, so you ought to have around 300-350 on the smoothing caps - if you have 220ish volts with the rf stage disconnected you either have a leaky cap or two to earth in the TB circuits, or a dried out electrolytic that is not passing muster.....

So, lets hear what is going on from these checks

Good luck

Sean

Re: Can somebody please repair My TV22
 

I do have an Avo but not here, will get it back tomorrow...

the HT does rise and drop off again.

Which HT am I measuring? Does an Avo have a 10kv range?

Thanks Sean...

Andi

Re: Can somebody please repair My TV22
 

Hi Sean, yes definitely low HT at only 195v, that's of one of the smoothing sides of the double can.

Need to do a cap hunt tomorrow.

But for now the bed is calling lol

Andi

Re: Can somebody please repair My TV22
 

Hi Andi,

DO NOT ATTEMPT TO MEASURE EHT!

Although it probably will not kill you, the risks are too great - if you do not know the dirty trick for measuring eht then just look for results on the tube.

Some terminology that I and others use.

LT - Heater supplies
HT - Anything that connects to normal valve anodes - up to approx 1Kv
EHT - Anything that is likely to leap off of things and bite you - over 1KV up to 40KV

If you get to SHT then we have gone into power generation and transmission, and shouldnt be discussing it here!;D

Ok, boring bit over.

Please measure the resistance between HT+ and chassis with the RF stage connected, and with it disconnected, oh and we could do with some voltages HT level off the cathode of the rectifier, and value after smoothing. - Resistances of less than 50K ought to be treated as suspicious.

Cheers
Sean

Re: Can somebody please repair My TV22
 

I would be looking at a couple of things here:

1. The smoothing cap - are you sure it is good? I've had problems with the units in these chassis before.

2. There are still alot of wax caps on the timebase chassis. Start by looking at the grid coupling caps on the sound, line and frame stages (the frame one is ISTR, a very large one). Leakage in these will cause the valve to conduct heavily and pull down the HT.

After you've checked them, work through the rest of the waxies! There are a lot on the RF chassis, but they are fairly easy to change, most, as I recall are HT decoupling ones (long time since I worked on one of these, and I don't have a diagram in front of me just now).

Jim.

Re: Can somebody please repair My TV22
 

And don't forget that wax capacitor that lives UNDER the TB chassis tagstrip.......

Phil.

Re: Can somebody please repair My TV22
 

Hi Guys, the only waxies left on the upper chassis are :

C51 - .001uf
C27a - .01uf (Brightness Control)
C49 - .01uf (Audio)
C27 - .01uf

I have now run out of caps so need to order some, Maplins don't do anywhere near the range they used to.

The main Dual can has been reformed but the 16uF one hasnt. (C63)

None of the caps on the IF panel have been touched yet as the HT is disconnected.

I will probably blanket swap the caps on that.

Andi

Re: Can somebody please repair My TV22
 

Hello again,

I know this thread is going to be a bit long but maybe this could turn into a restoration guide for a TV22, as I haven't been able to find one and these are extremely popular sets.

OK I now only have C51 left to change of the waxies on the upper chassis.

I now get this result with only the brightness control really making any difference to the line.

I still only have about 195v and 250v on the cathodes on V10

Now I disconnected the frame oscillator transformer (T4) and can get a reading of 573r on one side but the other side the meter can;t get a stable reading, is this fried? As this, I think, would account for the frame collapse?

Andi

Re: Can somebody please repair My TV22
 

Andi,

don't give up hope yet, it looks like you have some frame ouput - a dead frame transformer normally reults in a single line across the tube.

Change that last cap, then check the values of the resistors around the frame stage - I suspect one of them may have been cooked by the high currents.

Jim.