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Bush CT187CS - Back to the fray!

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Katie Bush
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Posted by: @jayceebee

Philips although one chassis did use one as a combined surge limiter and degauss. They were prone to fuse blowing, if you removed one you gave it a shake and if it rattled it was faulty.

Would that be the KT-3 by any chance? I remember them using a three legged 'mushroom' on the PSU daughter board.

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Posted : 20/11/2020 11:41 pm
Jayceebee
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Pretty sure the KT-3 used a dual posistor but for degauss alone. I think it was a portable chassis, maybe the CF1 that employed it in a dual role with surge limiting. I’m sure Sideband or Red to Black can confirm if this was the case.

John.

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Posted : 21/11/2020 1:35 pm
Katie Bush
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Posted by: @jayceebee

Pretty sure the KT-3 used a dual posistor

Hi John,

You're right, it did, as R2B told me earlier. I just remembered the white three legged mushroom and without thinking, I just put two and two together - and came up with five! And hang it all, I have two or three KT-3s, I just haven't lifted the back off one in over fifteen years!

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Posted : 21/11/2020 1:46 pm
Jayceebee
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Had a trawl through old PTV mags online just to convince myself I wasn't imagining it and found this, it seems it was the K40 and not the CF1 that used a combined degaus/surge limiter device. Not a dual posistor as the surge limiter needs to be an NTC element.

Degauss

John.

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Posted : 22/11/2020 10:06 pm
colourstar
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Back to the A823 power panel and I notice on my spare panel that diode D2 has been replaced with a wire link and R8 beneath it is deleted. Any idea what purpose this mod might have had?

Steve

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Topic starter Posted : 23/11/2020 4:27 pm
Jayceebee
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One of a number of mods to improve regulation and try to get rid of flutter which plagued this design, with D2 removed R8 was superfluous. You’ll find D2 is now in series with R11.

John.

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Posted : 23/11/2020 4:41 pm
colourstar
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Thanks John- your memory is excellent! Sounds like a worthwhile mod for the board I'll be using then.

Steve

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Topic starter Posted : 23/11/2020 4:48 pm
crustytv
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PSU mods covered on page 14 here 👍

Crusty's Collection: Read the repair blogs
Crustys Youtube Channel: If you want to follow me on Youtube, please consider subscribing
Vrat FaceBook: Follow us

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Posted : 23/11/2020 4:58 pm
Jayceebee
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Thanks Steve but it wasn’t from memory, I have two A823 sets to look at and have been reacquainting myself with its design, go to end of section H of the manual in the library.

Edit: crossed with Chris 👍

John.

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Posted : 23/11/2020 5:11 pm
Jayceebee
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8R13 to 1K as mentioned it the PT article does indeed make a very worthwhile improvement and would be the first I myself would implement.

John.

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Posted : 23/11/2020 5:59 pm
colourstar
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Happy to say that with the power supply panel revived with new thermistors the Bush is back in business and I'm very happy to say that the decoder panel did not receive a mortal blow during the dramatic flashover. Still further work to do including replacing the very worn on/off/volume pot and also going over the timebase panel as the frame hold is a bit bouncy. The focus is never that great on this set despite an excellent crt. I can also see flyback lines on a blank raster. I don't know if it's a peculiarity of this chassis but the brightness and colour controls seem to have a very limited range. The sound is excellent though.

So along with Chris's example that's two CTV187CS's ready for Christmas in Colour (actually I'd better not tempt fate, there are still a few weeks to go).

Also I have to agree with the comments elsewhere regarding the el-cheapo Chinese modulators. They really are quite poor. The picture and sound on the Bush are much better when used with my Panasonic vcr as a modulator.

Steve

Revived3
Revived2
Revived4
Revived1

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Topic starter Posted : 06/12/2020 6:03 pm
ntscuser and PYE625 liked
PYE625
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Looking splendid !

That bowl of fruit looks tempting.... might nick an apple whilst the test card is on. 😉

To understand the black art of electronics is to understand witchcraft.
Andrew.

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Posted : 06/12/2020 7:39 pm
colourstar
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Posted by: @pye625

Looking splendid !

That bowl of fruit looks tempting.... might nick an apple whilst the test card is on. 😉

You are very welcome Andrew, although you might find it a bit chewy. It would certainly last you right through The Two Ronnies...

A bowl of plastic fruit somehow seems in-keeping with the period though doesn't it? It was destined for a house clearance skip but I intercepted. I'm rather proud of it!

Steve 😀

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Topic starter Posted : 06/12/2020 8:09 pm
PYE625
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Haha....it certainly fooled me, thought it was all real. 🤣

To understand the black art of electronics is to understand witchcraft.
Andrew.

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Posted : 06/12/2020 8:22 pm
Jayceebee
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Looking very good 👍 . From the factory with the front colour control there was often only just enough to give ample colour saturation at maximum, I'm pretty certain the brightness didn't do an awful lot and was prone to flaring on whites at maximum on 22" and above CRT's. If my memory serves me right there is a preset colour control on the decoder but again at maximum some customers still moaned that there wasn't as much as other manufacturers.

For flyback lines try unplugging the RGB leads to the tube base from the decoder, if you can still see some illumination of the CRT then back off the A1 voltages until you just have cutoff. Best done in a darkened room.

Edit. I'm wrong. The preset colour control didn't appear until the two chip decoder arrived.

John.

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Posted : 06/12/2020 10:09 pm
colourstar
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I've been watching a couple of light entertainment shows (from 1970) this evening, featuring plenty of music. The sound quality on this set has a lovely warm bass quality and goes pretty loud, despite the loudspeaker being nothing special. Very good solid cabinets on these sets, by the way.

As per John's comments, even with the colour control on full, the picture is by no means oversaturated.

Posted by: @jayceebee

For flyback lines try unplugging the RGB leads to the tube base from the decoder, if you can still see some illumination of the CRT then back off the A1 voltages until you just have cutoff. Best done in a darkened room

Excellent, thanks for the tip! I'll do that.

Steve

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Topic starter Posted : 06/12/2020 11:09 pm
Katie Bush
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Posted by: @colourstar
Posted by: @pye625

Looking splendid !

That bowl of fruit looks tempting.... might nick an apple whilst the test card is on. 😉

You are very welcome Andrew, although you might find it a bit chewy. It would certainly last you right through The Two Ronnies...

A bowl of plastic fruit somehow seems in-keeping with the period though doesn't it? It was destined for a house clearance skip but I intercepted. I'm rather proud of it!

Steve 😀

My granny had a similar "Carmen Miranda" fruit bowl display on top of the sideboard, but hers were made of wax - I supposed they'd have melted on top of the telly. They were, however, very lifelike!

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Posted : 07/12/2020 7:19 pm
Nuvistor
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The photos of the colour pictures on the set seem about right for this model. They were never the most striking of pictures when new so I think you have it just about right. We sold these but customers preferred pictures on the Pye 691/3 chassis.

I could never understand RBM, they had lots of experience with CTV and their first commercial effort the CTV25 produced a reasonable picture but had the infamous LOPTX. Luckily I never had that problem and the Davy lamp was retro fitted to those we serviced. 
Then the the next model with the SL901 chip with its mediocre pictures compared to other makes, not just Pye. The comment from the salesman, trying to persuade how good and safe they now were was that RBM were using Quadruplers not Triplers that other companies used for EHT.

Still it’s nearly 50 years old, it still works so they must have done something right.

Frank

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Posted : 08/12/2020 4:36 pm
colourstar
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That's an interesting insight Frank. I think watching the Bush in isolation it looks quite good, but viewing it in a showroom line-up with other contemporary sets would have perhaps made it look a poor relation. I've never seen a working Pye 691 in the flesh but Andrew's set that we've seen on here looks superb and I know the earlier CT70 dual-standard models were particularly well regarded too.

I quite enjoy owning examples of flawed or inferior designs- it would rather boring if every make and model produced perfect results!

Steve

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Topic starter Posted : 08/12/2020 9:53 pm
irob2345
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Posted by: @colourstar

I quite enjoy owning examples of flawed or inferior designs- it would rather boring if every make and model produced perfect results!

Yes I get this! I once bought a Riley RMB in pieces for that reason! But conflicting priorities meant I never got to finish that project. I now drive a Lexus IS-250. I have little patience for imperfect cars!

The closest to a perfect CTV IMHO is still the Oz Kriesler 59-1 chassis, based on the Philips K9. Among other features, the horizontal AND vertical S correction is modulated to compensate for the varying amounts of S correction needed at the middle and the edges of the scan so that lines on a test pattern are ruler-straight over the ENTIRE screen. Not a bad effort for a 110 degree delta.

Mind you, you can only tell the difference on a test pattern!

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Posted : 09/12/2020 12:40 pm
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