Notifications
Clear all

1970 HMV 2703: BRC/Thorn 3000 MKII Chassis

Page 1 / 5
 
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

Not been active at the repairs and Its been a while, the last set on the bench proper was the Baird M702 briefly followed by the CU2213 Rediffusion MK1, that was back in October 2015. In an attempt to rekindle the mojo I thought about an Easter project.

The Candidate

For a long time the HMV 2703 has been looking at me, almost goading me to take some pain. You see its the the third and final set from the Crusty, Rusty sets I got a couple of years ago. You may recall these sets, they were the following :-

Ferguson 3713: 8500 chassis 

Multi-Broadcast 7773: 9000 chassis. 

These sets including this HMV 2703, had been stored in a metal shed for twenty plus years. As a result condensation damage to components on the other two were rife and I expect no less from this HMV. I was also aware that the CRT on the HMW like the Ferguson 3713 was last known to be pooped.

The 2703 is a 19" Colour employing the Mark II 3000 Chassis. I must admit one of my favourite chassis' to work on even though they have given me a little grief in the past.

hmv2703a.jpg

As you can see below, the cabinet is OK and with a little attention I think it will come up a treat. I even have a NOS Colourmaster badge to replace the one that has gone rusty. I bet the Thorn tuner will need those plastic lugs replacing.

2703-1.jpg

Well should I? Shouldn't I?.......... OK then

Set the Controls for the Far Side......

As has been my tradition we shall travel back so I pull the dusty tarpaulin from the crustytv time machine, blow the cobwebs from the controls and set the switches for the 26th of October 1970 ( the day this set has stamped inside). The lights in the workshop dim as the C.T.M. winds up to transport me back to 1970. As the lights in the workshop return to normal the radio can be heard playing the current number one, Freda Payne "Band of Gold", this was top of the hit parade sitting in the top spot for 6 weeks in Sept/Oct 1970.

payne.jpg

At the movies?

Well it wouldn't be the UK or the 1970's without the two new releases this year from the "Carry-On" team,

Carry on up the Jungle and  Carry on Loving.

On the TV?

BBC1

BBC2

ITV

Back to this HMV

A visual inspection, well like the others from this source its dirty and rusty, It looks to have had a lot of hours too. There's a couple of wires sprung loose from the line timebase module and one of the arms that hold the MK1 convergence panel in place, has rusted completely away.

2703-2.jpg2703-3.jpg2703-4.jpg

2703-5.jpg

2703-18.jpg

2703-6.jpg2703-7.jpg2703-8.jpg2703-9.jpg2703-10.jpg2703-11.jpg2703-13.jpg2703-14.jpg2703-15.jpg2703-16.jpg2703-17.jpg

As I mentioned before I was aware from the previous owner, that the CRT was pretty much duff. The A49 120X is not the original, it seems to have been replaced with a Granada tube in June of 1977. I have a spare NOS 19" A49 192X which will fit so that's the plan but first I thought I would see what the B&K makes of this Granada tube.

Here I ran into the first problem and not one of the TV's making, my trusty B&K decided that the Blue meter would develop a sticking needle fault. To be fair this had been brewing for a time and today it decided it was going on strike. Luckily I have a spare so that was the first job and the subject of the next post......

ReplyQuote
Topic starter Posted : 26/03/2016 4:21 pm
Topic Tags
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

As mentioned in the previous post a little transplant surgery was required in the B&K before I could ascertain the health of the Granada tube, so here we go on a slight digression but we're OK with that here.

The B&K was simple to open up, remove the four feet and the retaining screw on the front just above the handle. You then need to remove the main control knob, Blue G2 knob and the set G1 knob. Remove the shaft retaining nuts, followed by the power inlet housing screws. You can now pivot forward the main control panel fascia for access to the meters.

2703-20.jpg2703-21.jpg2703-22.jpg2703-23.jpg

2703-24.jpg

The new meter was a quick install as there were only two wires which are bolted to the terminals and just two bolts holding it to the fascia. Job done and the new meter is working and importantly not sticking. Next post I will deal with testing the Granada CRT.

ReplyQuote
Topic starter Posted : 26/03/2016 4:30 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

Granada A49 120X Test

With the B&K fixed I could now test the CRT, as expected it was very, very sickly, I left it a couple of hours simmering and on a slightly higher filament voltage.

2703-12.jpg2703-27.jpg

As can be seen from above, Red and Green were bad with Blue the sickest. So next task was to run a clean and balance on all three guns to see if that could improve things a little.

2703-28.jpg

Red and Green responded to this procedure rather well but Blue was stubborn, it was not having any of it. Ok so Blue is going to get a tickle to see if we can wake it up. I'm not too bothered if the CRT fails as mentioned above I have a nice NOS 19" waiting in the wings. 

I bopped the Blue and as can be seen below it responded favourably to this. The tube won't be the greatest but It will allow me to proceed to the next stages without having to change the CRT just yet, that can wait until later.

Red, Green and Blue are now acceptable

2703-29.jpg

This is the NOS 19" waiting in the wings and tested.

2703-25.jpg

What's Next?

Well the supply rails via the power module, 240V. 6.3V, 30V and 58-65V. Hopefully the chopper transistor is OK. The PSU module will be tested out of chassis on my Thorn test Jig ( see below). Once I have the status of the rails established the LTB can be introduced to the PSU via the jig where I can test its power rails and the line frequency. That will form part of the next post.

thorntest1.jpg

ReplyQuote
Topic starter Posted : 26/03/2016 4:51 pm
Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered
Posts: 5477

Thorn 3000 power supply.

I don't know whether to hide behind the settee or get the popcorn out...Confused

ReplyQuote
Posted : 26/03/2016 6:42 pm
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

I have the very same set here Chris. It needs setting up because it had a regunned tube fitted before I acquired it.

ReplyQuote
Posted : 26/03/2016 7:30 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

Cathovisor said
Thorn 3000 power supply.

I don't know whether to hide behind the settee or get the popcorn out...Confused

 

OH you ain't seen nothing yet!! This TV does not disappoint from its source, its as crap as the other two sets, if not worse. I don't quite know where to start explaining this one.

First the intriguing bit which is about the only positive thing I've to say about this module. I've not come across a 3000 PSU module that employs 4 fuses (F606&F607 additions) or if I have, I've forgotten about it. I've not found any mention in the 3000 service manual yet either.

It's a 296D and well what can I say, its been well and truly got at and I mean "GOT AT!"

There are many components that are badly tacked in, some wrong values, a broken PCB which has had a failed repair attempted. Many other components have broken pads, the Chopper transistor is rusty as they come. C624 so loosely tacked in it can and does short to chassis. The harness connector has been bodged up with solder, these were readily available as replacements back in the day and I have a few now, so what was the excuse back then? The main TX is rusty and the mounts perished, the whole TX rocks about. The module has a sticker stating " 25th Feb 1981, last time it was in for a proper service?

I have to say the "engineer/s" who worked on this at the end of the sets life, look to have little pride. I appreciate some worked to schedule but even so I think they would have made a better job. This does not feel like a professional mans work but smacks of the backstreet bodger or the rank careless/clueless amateur.

The module is a pigs ear, to be honest I'm not going to waste my time on it as I just know the grief it will bring. I will harvest usable components for stock, that's all its good for. I have a couple of other PSU modules, non workers but in far better condition. I will use one of those to progress this set further.

2703psu1.jpg2703psu3.jpg2703psu2.jpg2703psu5.jpg2703psu4.jpg2703psu7.jpg2703psu6.jpgconn.jpg

ReplyQuote
Topic starter Posted : 26/03/2016 7:57 pm
Mikey66
(@mikey66)
Active V-Ratter Registered
Posts: 193

I've seen those edge connectors soldered up like that before Frown

I always thought it was far easier to retension the socket with some long-nosed pliers

ReplyQuote
Posted : 26/03/2016 8:04 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

Perverse curiosity, "a come hell or explosions" mentality took hold so it was plugged into the test jig. Finger in one ear the switch was flicked, to my amazement despite all the carnage of broken PCB, loose components and appalling condition, the 6.3V rail came up as did the 30V rail, leaving only the 58-65V rail dead but that's not there as I've not hooked in the LTB so the pulse from the osc is not present to trigger the monostable. Not even looked at the LTB yet, of course the rail may be missing due to W605 which is rattling about on one end. Hardy little blighter's the thorn PSU's. 

Still don't think its worth faffing with though as it would require major reworking to get it into half decent shape. Then there's the big crack, I'll sleep on it, but it was fun to see it powered and satisfied my curiosity. 

ReplyQuote
Topic starter Posted : 26/03/2016 9:04 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

Removed the Line Timebase module and that again has suffered from the moisture, makes you wonder how the Jelly-pots have faired. In places looks cooked to a crisp, the driver stage transistor VT503 was completely dry jointed and could be plucked out, as could the efficiency diode W504. These were soldered back in circuit.

Looking under the Beam limiter circuit board I found a wire had been cut ( see last photo below). I believe this lead is a 30V feed to the LTB board, I wonder why it was snipped?

What a mess a!

Still in the gung-ho mode I connected the LTB to the PSU, the PSU to the test jig and the pulse lead to the cathode of W608. What are the chances of this all working and the 58-65V rail coming up? Not a lot it was still dead, well we didn't expect it to be that easy now did we.

Could be a myriad of things, I would need to remove and check VT504, if its OK leave the collector disconnected whilst testing. Check why it appears the 30V rail has been snipped, get the 30V and 60V rails stable on the LTB and if I get that far scope the osc.

That's it for now, as I said at the start of this thread, this set like the other two was always guaranteed to be a dog. God knows what I'm going to find on the I.F, Video, Chroma, Convergence, Field and sound boards. Not sure what I'm going to do yet, whether to proceed with the modules at hand, plod on trying to fix these or find some new better ones from my stores, maybe just go out and stick my head in a bucket and hope it goes away. only kidding.

As I've said before and I will say again if you have sets in a leaky shed damp garage, think again as this is the result.

This thread like most of mine will no doubt go on for a bit Wink

2703ltb-1.jpg2703ltb-2.jpg2703ltb-3.jpg

ReplyQuote
Topic starter Posted : 26/03/2016 11:18 pm
sideband
(@sideband)
Famed V-Ratter Moderator
Posts: 3971

With bodges like those, it will never be reliable even if you can sort them out....it won't be worth putting the back on! Best to look for better boards and fix those.

ReplyQuote
Posted : 27/03/2016 2:22 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

Hi Rich,

I'm inclined to agree with you 100% and I think I know why I left this waiting for so long, I had a feeling it would be bad. The other two sets were crusty and rusty but this has been well and truly visited by uncle bodger.

Later today I will remove the rest of the boards and report their condition here. It will be interesting if not sad, to see what other carnage has been visited upon them. I just don't understand the mentality of people who bodge makes me so angry Yell

This set is likely to be "Triggers Broom", if it were not for these sets being thin on the ground, I would just scrap it as a lost cause.

ReplyQuote
Topic starter Posted : 27/03/2016 2:36 pm
Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered
Posts: 5477

crustytv said
 I just don't understand the mentality of people who bodge makes me so angry Yell

There's a lot of bodge artists still about, sadly. The work here looks like it was done by the sort of back street outfit that advertised in the small ads in the local papers giving "free estimates!" and very cheap work, which consequently relies on considerable turnover to make any money. Given it was done in 1981 - when realistically, the set was by any stretch of the imagination life-expired - it's done with "I don't want to spend anything on it" in mind. Perhaps it belonged to a really cheap rental outfit.

ReplyQuote
Posted : 27/03/2016 3:34 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

I've removed all the other boards and thankfully they are in far better condition. There are a few components that have been replaced badly, on the whole they remain pretty much in original condition.

a-1.jpg

a-2.jpg

The I.F. board has a couple of iffy tacked in caps, the field/sound board has some cooked caps and resistors. On the chroma board  L305 looks to have green infestation so it might need replacing. All in all they should with a little effort, be usable.

I.F. Board

a-3.jpg

a-4.jpg

Video Board

a-5.jpg

a-6.jpg

Chroma Board

a-7.jpg

a-8.jpg

a-9.jpg

Field and Sound Board

a-10.jpg

a-11.jpg

Convergence Board

a-12.jpga-13.jpga-14.jpg

ReplyQuote
Topic starter Posted : 27/03/2016 6:30 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

This evening I dug two candidates out from the stores and a little work later I have a working PSU and Line Timebase modules. As can be seen from the photo, all rails (240V, 6.3V, 30V and 58-65V) are present and correct.

The LTB oscillator is running, I scoped the output from VT502 collector, although as you can see its a little off at 13.6KHZ this was evident to my ear too.

psultbscope.jpg

ReplyQuote
Topic starter Posted : 27/03/2016 10:14 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

Whilst repairing the focus lead which was poorly soldered to the CRT base PCB, I noticed the tuner/Aerial socket had seen some prior attention. At some point in this sets chequered past a new tuner has been fitted, rather than doing the job properly it was done badly.

The sets original aerial socket, has the original supply lead (brown) this would have come directly from the tuner, bodger has cut it. The new tuner which has the lead for the aerial socket should have been soldered to the back of the sets aerial socket, nope it was just twisted together with some electrical tape to the snipped feed. Class!!! 

aebodge.jpg

ReplyQuote
Topic starter Posted : 27/03/2016 11:59 pm
Tazman1966
(@tazman1966)
Reputable V-Ratter Registered
Posts: 374

Wow! Some rough work has certainly gone on there. How much of a hurry was the bodger in with this poor set? Good luck with it Chris.

 

Tas

ReplyQuote
Posted : 28/03/2016 12:52 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

In the grand scheme of things on this set considering the other faults, unimportant. However, 10 mins spent doing the right thing........... Even back in the day not a costly exercise in time or materials. 

ae.jpg

ReplyQuote
Topic starter Posted : 28/03/2016 10:04 pm
Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered
Posts: 5477

crustytv said
In the grand scheme of things on this set considering the other faults, unimportant. However, 10 mins spent doing the right thing........... Even back in the day not a costly exercise in time or materials. 

Playing 'Devil's Advocate' for a moment... six lots of ten minutes is an hour. That could easily translate into two "easy fixes" (e.g. the boost C on a Decca 'Bradford') that would generate more money for the company than those ten minutes spent on making a job tidy would.

I've worked with people with no pride in their work - the response was "It still works, nobody sees it, who cares."

ReplyQuote
Posted : 28/03/2016 10:47 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

Some cold checks of the other panels prior to first application of power.

On the video board C206 (400uF) which decouples the 30V rail and C222 (1uF) in the Blue colour diff circuit were replaced, both having puked. There's a couple of other which I'm in two minds about then there's all the tant's, I think I will leave them for now for fault finding exercises rather than shot gunning them all.

On the Field board a lot of the caps look to have age to them and look rough but non have puked so I will leave them for now also. R451 (910K/1W) however looked like it had spent the last 45 years down a coal mine. This is in the -800v feed to the LTB. Once removed it was found to have more than doubled in value, so was duly replaced.

The chroma board, lots of tants and some rough caps but no pukers, again these will be left for fault finding. W322 (OA91) the pulse clipper, was found to be o/c  so was replaced.

The I.F. and convergence again same story, nothing too untoward.

Hopefully later today application of power with the tripler disconnected and we shall see if the magic smoke escapes.Cool

ReplyQuote
Topic starter Posted : 29/03/2016 1:06 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10842

Almost ready for power up, I won't variac will just go full beans and see.

My reasoning?

Firstly the PSU and LTB have been tested at 240V already on the Thorn Test Rig. That showed the power rails were all present, correct and ran for 20 mins or so whilst I scoped the Line frequency which was slightly off at 13.6KHZ. So I'm fairly confident the main supply is fit to go. 

Secondly I've gone over the other modules and did some cold checks replacing the minimum that were needed i.e puked caps etc.

The tripler will be disconnected, if I get past that stage without dramatics I will connect the tripler. I have the in-line EHT meter connected should I get that far so as to watch for too high or too low EHT.

prepwr2703-1.jpgprepwr2703-2.jpg

ReplyQuote
Topic starter Posted : 29/03/2016 3:00 pm
Page 1 / 5