Newbie to the forum - Baird 3000 chassis

Hi 70,

Welcome to the forum.

Just a pedantic point, its a Thorn 3000 chassis not Baird 3000 chassis (see * below).

As you may or may not have already noted, there is a wealth of Thorn 3000 information here at Radios-TV /Vrat. I suggest the first thing you do is plough your way through a good part of it before even attempting another power up. This chassis is probably not a good one for a newbie to start however, If you go to the Blog home page here. Scroll/swipe down the page and you will find the Thorn TV block. Click or tap on the Thorn contents link and it will expand some of the resources, will see there is a link top show all 34 articles.

These resources will provide you will a mass of information and I would say required reading. The 3000/3500 diagnostics is a very good one as it clearly lays out a logical fault finding guide and symptoms. There's also a complete description of how the Switch Mode PSU works. There is the Trader 3000 service sheet which although not as good as the Thorn manual, is a good starter cct.

You will also find CTV stock faults here, the Thorn 3000 you're interested in is there.

You may also find all my past Thorn 3000/3500 PSU repair blogs useful reading, I also go over how its supposed to function. You need to understand how it works otherwise you'll be chasing your tail.
https://www.radios-tv.co.uk/thorn-3000-psu-repair-blog/

I've also covered the PSU in a YouTube series if you can stomach my boring voice and lack of comfort talking to a camera. It might not be the best example as it had very little in the way of faults but I do go over its function.

As I've hinted at above, the 3000 PSU is not for the fainthearted, they were loathed by many but I think they are one of the best chassis' to work on and once you get to know their oddities, they become less intimidating. It was certainly the most prevalent chassis to be found in the UK at the time.

Posted by: @19seventie

(Just out of curiosity, what would it's value be? I know the first Baird colour sets are valuable so I'm curious to know and compare)

The simple answer its not in the same league as the Baird 700 series colour TV which I believe is the one you are referring to as "valuable" nowadays. The 700 series was a Radio Rentals designed chassis with the help of RCA, designed for the launch of the colour service.

*The 700 series chassis is completely different beast to the Thorn 3000 chassis, it has valves for a start. There had not been a true Baird Television for many years, Radio Rentals owned the "Baird" name (badge engineering). After the 700 series they briefly used the Thorn 2000, then in 1969 decided to populate their "Baird" range with Thorn 3000 chassis. Thereafter came the 8000/8500 etc. Oh and Radio Rentals briefly for a 19" Baird marketed as the cheapest colour TV for 1967, used a GEC 2028 chassis.

Welcome 70,

Chris as lots of experience with this chassis and the documents he referred to are well worth reading.

Thorn sets were not one I came across very often, only saw one 3000 chassis. It was a PSU fault and I took the easy way out, I was about 2 weeks away from leaving the trade so I got an Advance Replacement from Thorn. I had no spares or service info so it was probably a wise decision.

I did see the 700 chassis but not repair them, they were capable of a superb picture.

Hi, Thanks for the welcome (And the profile picture, funnily enough the MK3 Cortina is my favourite cortina)

My bad with the title, I wrote it with meaning that it's a Baird, using the 3000 chassis, but poorly written - That's what I get for trying to write at 3AM haha

I've read most of your blogs and some quite a few times, but I'll definitely be reading them more as I know they'll be of great help, especially of course the 3000, though I can't say I've read through the CTV stock faults, not that I remember anyway. It'll be a long journey to completion as I don't have everyday access to it nor do I know 100% exactly what to do with it, it'll be fun though to work on it and learn on the way

Somehow I've never found your YouTube video, even though I've searched on YouTube before for the 3000 chassis, never found much though. I'll give that a watch after posting this, I'd certainly like to learn more about how they work as I understand they're a little bit different than most power supplies. 

It might be to my benefit that I've not worked on too many others and therefore not expect it to be a certain way, like most other sets, and just accept the oddities for what they are as I know no different. We'll soon find out.

I 100% understand that the 700 and 3000 chassis are in different leagues, I was just curious as to how they compared from one another, although only being a couple years apart. I was hoping it'd be a 700 chassis, but I'm still happy to have this 3000. As I say, was only curious.

(I intended to add photos to my first post but somehow failed) 

Thanks
'70

That model is the 8726, if you've not seen the brochure for it, they can be found in the brochures section of the blog covering hundreds of period TV's. Here's a shortcut to the Baird one, scroll down and you'll find it.

I've got two 3000's in similar cabinets, the 1969 8724 and the 1972 8749. I think as consoles go Radios Rentals made a fabulous style cabinet that as you noted, carried through from the 700 series.

https://www.radios-tv.co.uk/baird/

Thanks for the pictures of the 3000 chassis. It brings back memories of the 3500 we saw briefly in Australia in 1974 when AWA were having trouble making enough 4KAs (4000) that would last more than a few days in a customer's home, so they imported some 3500s from the UK. Our 3500s had a mains transformer, as did the 4KAs.

All local factories were running 3 shifts 7 days a week to try to meet the demand for colour CTVs. Brands with international connections used them to supplement local production.

The company I worked for used 3500s for rentals - they were all we could get at the time. Most were retired from the rental fleet after 6 months. I bought a few very cheaply for friends and family. The early ones had Mazda CRTs that faded away after a year or so. Later shipments had Sylvania CRTs that were brighter and lasted a lot longer.

A few years later I successfully transplanted a self-converging CRT and yoke into a 3500 which served as a 2nd set for my sister-in-law for many years. The big convergence flap was removed and the HT was turned down to about 50 volts to get the EHT and width optimal. Everything ran much cooler.

@irob2345

Thorn owned quite a few rental companies or had connections to them. Thorn dominated the UK rental market so there were probably more Thorn CTV sets in use than any other make in the 1970’s. 
We had RBM (Bush/Murphy), Pye/Ekco, ITT, Toshiba and Hitachi. We also had Roberts and Dynatron but these were a Pye or Philips chassis.

All had their foibles, we took on ITT due to the dire Pye 697 chassis, what were Pye thinking of when the 691/3 were decent. The Pye 725 transistor chassis I found decent, the 110 degree version 731 not so much. RBM were going down the same path with some models T20?, I forget. We took on Toshiba and Hitachi, excellent sets to start but by the end of the 70’s reliability was nowhere near as good as the earlier sets.

Still it kept me in a job in the 1960’s through the 70’s, can’t complain too much. 

Posted by: @crustytv

That model is the 8726, if you've not seen the brochure for it, they can be found in the brochures section of the blog covering hundreds of period TV's. Here's a shortcut to the Baird one, scroll down and you'll find it.

I've got two 3000's in similar cabinets, the 1969 8724 and the 1972 8749. I think as consoles go Radios Rentals made a fabulous style cabinet that as you noted, carried through from the 700 series.

https://www.radios-tv.co.uk/baird/

Sorry for the late reply

Thanks for linking those, I really enjoyed looking through the Bairds, and all the others. Have to agree with you on their cabinet designs, The 8724 is probably my favourite out of those with the 3000 chassis, but for their general console design, the M702W has got to be my ultimate favourite. 

irob, that's a really interesting story. I'd have loved to have been around in the 60s and 70s during the colour boom, must've been exciting really. Interesting you mention the Mazda CRTs, as mine still has a Mazda fitted, which I know aren't the best of CRTs, not for longevity anyway. Although I think the people I bought it off said they weren't massive TV watchers, so fingers crossed it's still got decent emission - I've not got a CRT tester, so the only way I'll be able to tell is when I get the set working. 

Edit: Sorry, I increased the text size while writing to see it better and didn't realise I couldn't get it back to default, is there any way it can be defaulted as I can't unless I go to small

Thanks
'70

Yes the colour TV boom allowed us to buy land and build on Sydney's Northern Beaches. God's own country! My wife was a high school teacher and they paid them well in those days too.

The company I worked for did warranty service on new TVs. And, in the early days, installations in homes. Favourite 1st gen colour TV? The Kriesler 59-1 110 degree Delta.

Evening all

In regards to the Baird set not a great deal has been done to it as I don't have constant access to it, so it's going to be slow progress. So far all I've really managed to do is fix the tuner controls and just try and get to know it a little bit more.

I wanted to change the green tuner capacitor as I know these are prone to failure and just wanted rid of to be safe. (Didn't realise there was one in there when I powered it up - it hasn't been powered up since) 

This is going to be a very novice question but I have to ask, how do I remove the PCB to unsolder it? I removed all the connections that I could see, as did I the PCB above it but it had very little freedom to move, and no where near enough to solder and unsolder. I also wonder if the whole chassis can and/or needs to be removed from the cabinet? I've not gone too deep into this set as it's really not something I'm used to and want to get this right, hence me double checking. 

I think it'd be easier for me to work on it with the chassis removed, and just putting it back when needed to test it out. 

Another query is what's the bare minimum I can do to get it safely running up for about 15 minutes max to test the tube? It's got a Mazda...

Thanks all
'70

I'll defer to others about the "bare minimum" question. It depends on what faults are in there. I've seen quite a lot on this site about fixing the power supply, probably the cause of most grief.

To work on the chassis there is no need to remove it from the cabinet. There are two (four?) little levers on the sides that allow you to slide the whole chassis back about 6 or 8 inches. The power supply and line modules unclip (once you remove the hex-philips transit screws) and they hinge back to get at the other side. You can then unclip them to remove them. There is really no need to unsolder anything, it all unplugs. All the plugs are different and /or are colour coded so you'd have to be a real klutz to stuff it up.

It pays to get a copy of the excellent service manual, which has instructions for setting up the many preset pots to get correct voltages. Do this properly and you'll have a nice TV.

The Mazda CRTs were a bit of a disappointment. Never very bright, the shadow mask would dome badly on highlights and the colorimetry was just wrong. If you can find a good Mullard CRT they are much better and the colours are very "natural". Later 3504s that we saw had Canadian Sylvania tubes that were nice and bright.

All the 3504s (a development of the 3000) we had in Oz were either branded AWA or Thorn. They were fitted with mains isolation transformers (so they were not live chassis) and had a resettable red button circuit breaker for when the crowbar fired off. I bet UK service guys wished they'd got those!

I guess we didn't regard them highly in Australia because we were dealing with much newer designs by the time colour kicked off here in 1974. They must have been the only colour set we saw in Oz without a single IC anywhere in it!

@irob2345

The UK set had the red cut out button, see one of the photos in a previous post, I have just checked the circuit to be sure, the transformer fitted in the UK set wasn’t an isolation type though.

I have not looked at the circuit before but an interesting item in the Television magazine Sept 1978 shows provision for VHF tuner, that itself isn’t a problem but it’s a valve VHF tuner, heater and HT supplies for the tuner are shown on the diagram.

What was the thinking behind that after all the work for a fully solid state CTV? Some areas of the UK required VHF capability for reception in areas that had communal aerial  systems, but why choose a valve type.

The Oz 3504 had a VHF turret tuner made by Matsushita. No valves though. It was a good tuner and those TVs had good sensitivity, important for rental fleet TVs.

Maybe it was a supply issue? The Pye T23 (1966) had a valve tuner as did a number of early hybrids.

@irob2345

Could be supply but the sets were released around 1969/70 and all other makes had transistor VHF tuners available. We will never know but I find anomalies like that interesting.

Posted by: @irob2345

I'll defer to others about the "bare minimum" question. It depends on what faults are in there. I've seen quite a lot on this site about fixing the power supply, probably the cause of most grief.

To work on the chassis there is no need to remove it from the cabinet. There are two (four?) little levers on the sides that allow you to slide the whole chassis back about 6 or 8 inches. The power supply and line modules unclip (once you remove the hex-philips transit screws) and they hinge back to get at the other side. You can then unclip them to remove them. There is really no need to unsolder anything, it all unplugs. 

Sorry for the late reply

I should clarify that I mean bare minimum as in is there anything that needs to be changed on sight, or at least an eye kept on, as I'm not familiar with these sets. As you say about the power supply, I did run it for a little while after removing fuses and plugs just to allow any caps to reform and help let it wake up a bit. That was only once and for a short amount of time. 

As for removing the PCBs, they came loose but looked to be held on with wires still, I'll get a photo up on Wednesday at the earliest. Perhaps a mod (Bodge) has been done?

Posted by: @19seventie

As you say about the power supply, I did run it for a little while after removing fuses and plugs just to allow any caps to reform and help let it wake up a bit. That was only once and for a short amount of time.

I think its worth pointing out for clarity in case "new starters" to the hobby or folk looking in think this is how to reform capacitors, it is not. Its so easy for info on the web to become fact and I do not want VRAT to be a source of inaccurate information. 

Lets be clear, with your practice all your doing is just introducing the electrolytics to full, brute force 240+V, you're not giving the dielectric any opportunity to reform whatsoever, that is NOT reforming! There's a procedure to reforming electrolytics, how and what you need can be found in discussions elsewhere within this forum.

The 3000 PSU is robust so you won't have caused any problems but as I say, what you did is not how anyone should approach reforming electrolytics nor be held up as one. The PSU multi-can, C202/C203/C206 should have been isolated from the power supply circuit and then reformed using a reformer or at the very least a voltage and resistance over time, whilst monitoring the current/leakage.

If you follow many of the restoration threads on VRAT you see folk like Andrew (PYE625), myself et-al, pretty much all follow this approach.

Its so easy to pick up bad habits, much harder to break them. I do hope that helps and the advice given is taken in the spirit it was intended  👍 

Recommended reading:
https://www.radios-tv.co.uk/community/in-the-workshop/new-project-capacitor-reformer/
https://www.radios-tv.co.uk/community/in-the-workshop/electrolytic-capacitor-reformer/
https://www.radios-tv.co.uk/community/in-the-workshop/project-leakage-tester/
https://www.radios-tv.co.uk/community/general-discussion/cap-re-former/
https://www.vintage-radio.com/projects/capacitor-reformer.html
https://www.6v6.co.uk/vcomp/tech_tips/reform_caps.htm
http://www.electrojumble.org/reforming.htm

Posted by: @19seventie

As for removing the PCBs, they came loose but looked to be held on with wires still, I'll get a photo up on Wednesday at the earliest. Perhaps a mod (Bodge) has been done?

The only parts that I recall which required some desoldering of leads to remove them from the chassis were the focus unit and I think the CRT base board. Also the beam limiter board if you wanted to remove it from the line timebase but in the vast majority of cases that would be unnecessary. 

if you did want to remove the chassis completely then it would be necessary to remove the plastic 4BA nuts securing  the user controls to the cabinet front and the screw securing the red button cutout on the rear. Again unnecessary in my opinion.

Please take heed of the advice about capacitor reforming. In some cases I don’t do it but I was in the game for 45 years. I didn’t take any risks with a Thorn1400 which I’m thoroughly familiar with, It has five capacitors in the same can and as it’s PCB mounted if one let go could result in major damage to the board. I’ve only seen one large multi electrolytic can explode, it’s not something I would like to experience again.

There’s a wealth of Thorn info and experience on this forum so you should be able to bring life back to this beauty.

Something I’ve spotted which will need attention later is the cable from the tripler to the EHT transformer. This should have a sponge sleeve around it to prevent corona discharge, the sleeve often disintegrated with age, it should always be replaced for safety and to prevent an interference effect on the picture known as ‘Brushing”. A small length of grey foam pipe insulation will suffice.

Posted by: @19seventie

As for removing the PCBs, they came loose but looked to be held on with wires still,

Both the PSU and the LTB (Line time-base) modules lift out but you still have to unplug some harness connections, these will most likely be the wires you state as still being attached.

Dealing with the PSU first;
you will need to unplug the umbilical lead that is attached to the PSU point PLG/3, this comes from the adjacent line-time-base module and is identified as SKT3. Then you will need to unplug the lead SKT1 which is in the 22/spade SKT2 socket, this is located in the left-hand side of the PSU module. With these disconnected you will now be able to fully extract the PSU module.

p.s.
Be careful when extracting the PSU module, its very easy to catch the transformer (T601) on the chassis frame. This can result in breaking the plastic surround where the winding taps emerge. Over time the plastic becomes brittle and is easily damaged.

Now the line time-base module;
as already discussed the flying lead SKT3 has to be unplugged from the PSU. Then you need to remove SKT27 which is the line scan out lead, this is a long lead that goes to the convergence board. There is also a grounding lead that goes to the CRT shield that needs unplugging. Now remove PL22 on the top, this goes from the harness to the Beam-limiter board that also resides on the LTB module. Finally remove the tripler lead from from T503, the EHT transformer. Now the LTB module will easily lift out.

In conclusion;
as I mentioned before the key to servicing/repairing the PSU is understanding how it functions and how the rails are dependant. The opening page of this thread is required reading to achieving that understanding.

https://www.radios-tv.co.uk/thorn-3000-psu-repair-blog/

Oh dear, forgot about the PSU which will require probably the most attention. Make sure you watch the Crustytv YouTube channel about the PSU and how to spatchcock it. 👍