Dynatron TV23A Falcon

A bit more work on the TV23A tonight.

I went over the top side of both chassis's with a soft brush and the hoover. It already looks a lot better.

Valve line up on the IF panel:

V1-V5 = 6F12 MAZDA

V6 = 6D2 MAZDA

V7-V8 = 6F12 MAZDA

V9 = 6D2 MAZDA

V10 = 6F12 MAZDA

V11-V12 = 6F12 MAZDA

V13 = EBC33 MULLARD

V14 = EL33 MULLARD

Valve line up on the timebase panel:

V1 = 6D2 MAZDA

V2 = T41 MAZDA

V3 = EL38 MULLARD

V4 = T41 MAZDA

V5 = EL33 MULLARD

Valve line up on the power supply panel:

V1-V2 = UU7 MAZDA

I have also discovered that this set and the TV21 do not have mains EHT.

EHT REC = EY51 MULLARD

I emailed Trevor today and have had a nice reply from him, he is going to look through his notes to see what he has and is also going to ask Mikeymushradio to see what he has. Trevor suggested to just gently wake it up on the variac in the same way he did on the TV21.

I have no means of testing a triode CRT, but the heater is intact and there is no leakage when I go round the pins with my Fluke so hopefully the CRT will be OK.

Posted By: TVJON74

I have also discovered that this set and the TV21 do not have mains EHT. EHT REC = EY51 MULLARD

Well I never, that'll teach me to ensure I always read threads THOROUGHLY. Indeed looking back at Trevor's posts, he too initially thought the set was Mains EHT due to the BIG TX's but posted that was not the case, I missed that!  ?  https://www.vintage-radio.net/forum/showpost.php?p=367034&postcount=12

That's a result and must make you feel a lot happier about tackling it, I know it would  for me.

Excellent news Trevor is on the case with regards to his notes and any other info to assist you. Looking forward to your progress.  ? 

p.s.

Hope the tube is OK

Hi Jon

So I presume everything is as it should be and there were no parts missing?

Whilst none of them pictures or any of what you said makes any sense whatsoever to me, am I to gather that the mains bit is not as dangerous as initially thought?

Wendy

Posted by: wendymac

Hi Jon

So I presume everything is as it should be and there were no parts missing?

Whilst none of them pictures or any of what you said makes any sense whatsoever to me, am I to gather that the mains bit is not as dangerous as initially thought?

Wendy

Hi Wendy,

Yes, so far from what I can see everything is as it should be and no bits missing. Also this set does not have mains EHT which makes it a bit safer to work on.

Just for background Wendy, older TV's with mains derived EHT (Extra High Tension) were dubbed as 'widow makers'! Basically it means that several thousand volts were obtained from a large mains transformer at several millamps….more than enough to kill if an unfortunate engineer should come into contact with it. A more modern approach was to obtain the 'EHT' in a different way which limited the current to microamps. It will still 'bite' if accidentally touched but is basically harmless and apart from a few well-chosen expletives, the engineer will be none the worse for wear. Most of us at some point have had an EHT shock from later sets and we learn to respect them and avoid further mishaps. 

Nice to hear Trevor mentioned again, still miss his input on the forum but I know he had lots of commitments.

 My earlier post about waking it up on the variac was based on the EL38 with the top cap wire disappearing towards the transformer shown on the initial pictures, I just guessed it was standard flyback at the time not realising that the mains EHT had been mentioned previously.

I had another email from Trevor a few days ago and it was not the news I was hoping for! Neither Trevor or Mike have any infomation on the Dynatron and Mike no longer has the TV21 either. Trevor has suggested a bit or reverse engineering and I had already started to think about doing this too if no information was available.

Today I removed the power unit from the set so I could start working out the power supply circuit. I was totally amazed at what saw! I have not touched the chassis or made any attempt to clean anything, it is exactly as I found it. I can't quite believe just how clean someting of nearly 70 years old could be. Its like it has just come off the production line.

One of the capacitors in the power supply is dated AUG 48 so the power supply could of been made before the timebase as one of the capacitors in the timebase is dated DEC 48.

Another nice feature I have found sice removing the power supply is a socket for powering an aerial amplifier along with the socket for connecting the power supply to the rest of the set.

Both fuses (one external 2A on the mains side and one internal 3A on the secondary side) are both intact, but the mains switch is open circuit and the rubber cable to the mains switch is also showing signs disintergrating so this will have to be replaced. The mains voltage selector has settings for 180, 200, 220 & 240 volts plus a second setting for 0 or +10, so this gives the option for voltages of 180, 190, 200, 210, 220, 230, 240 and 250 volts.

The power supply consists of 3x mains transformers, 2x UU7 rectifiers, 5x capacitors and 2 resistors. A very well built unit of what looks to be top quality.

OMG! That power supply does indeed look new!

It certainly suggests this TV is possibly a very low hour set, perhaps only used for special occasions or events and of course the Queens Speech. Dare we assume/hope that means the CRT might also be virtually unused too? Lets hope so.

Look forward to your updates Jon, this is shaping up to be one of the most interesting TV threads in a long while, the sort of treat we used to get from Brian.  ? 

Posted by: Chris

It certainly suggests this TV is possibly a very low hour set, perhaps only used for special occasions or events and of course the Queens Speech. Dare we assume/hope that means the CRT might also be virtually unused too? Lets hope so.

This is shaping up to be one of the most interesting TV threads in a long while, the sort of treat we used to get from Brian.  ? 

 

I do hope so Chris!

Until the set has power or I can find a tester for a triode CRT I won't know, but I am hopefull it will be OK with what i have seen so far.

I so wish Brian was still with us. I am no where near his skill or knowledge. I just hope I can do the set justice.

With regards to checking the CRT's emission, can you not utilise this ?

https://www.radios-tv.co.uk/build-a-simple-crt-tester/

Thanks Chris, that is certainly worth a try ? 

I should add I now own the set that Trevor worked on: but no service information came with it other than the radio chassis info. 

I'm not sure what is happening with Brian's information library but I can try and find out. 

Hi Jon

Just to jump in and give you a bit of background, the TV has not been switched on for approx 40 years. After my friend's father died, her mother banned the use of all electrical items in the home. I believe it had something to do with her faith. When her mother died, she then obtained a small tv which she watched occasionally so I am not surprised that it's so lovely and clean tbh. I would also presume that even when they first bought the tv, it was probably only ever used about once a week going on what the lovely Sandra told me about her past.

Edit................. just worked out the dates, more like 50 years!

Wendy

Posted by: Cathovisor

I'm not sure what is happening with Brian's information library but I can try and find out. 

That would be great Catho. Thank you ? 

Hi Wendy,

Thanks for the background.

That would explain why its so clean inside.

Posted by: TVJON74

The power supply consists of 3x mains transformers, 2x UU7 rectifiers, 5x capacitors and 2 resistors. A very well built unit of what looks to be top quality.

I would like to make a correction to the above. There is only one mains transformer, what I originally thought to be two smaller transformers are in fact chokes.

Hi Jon.

I am glad you have been able to get a good look at the set. Cathovisor should be able to help you, I didn't realise Mike had passed the set to him so it's in very good hands. The biggest issues I had was the controls and neither myself or Mike had suitable replacements, the other issue was the scan coils and again there was no direct replacements, an additional frame output transformer and different coils were used but it was a bit of a compromise.

I actually think I have Mikes original coils here after looking at your photos. These sets are well made and a slow run up could yield some results.

I'm watching this thread and hope you get some results soon.

Good luck.

Thanks Trevor,

I noted that you has problems with the scan coils.

I am currently working through the power supply and drawing the circuit as I go. The mains transformer is enormous!

So here is the power supply circuit.

I have no idea as to what the values of C1 and C3 are supposed to be. They are big "metal can" types with screw terminals, C1 measures 3.7uF and C3 measures 4uF.

I have included pictures with component ID's for reference.

I now know the values of C1 and C3 (as shown on my circuit). They are both 4uF. I could not see the printing for dust and that the printed side was up against the mains transformer and one of the chokes.

I have never seen capcitor's with working voltage depenent on temperature before either. Also odd that TCC used both °C and °F on parts that were (presumably) made at the same time. The smaller (C3) capacitor also has 4812 stamped on it, would this be DEC 1948??

I have updated the circuit with the values of C1 and C3.