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Old 7th Oct 2017, 6:52 pm   #1
slidertogrid
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Default Bush TV135RU missing valve ID

I have recently bought a Bush TV135RU. Today I had a look inside. Both scancoil plugs are unplugged and it has a valve missing, other than that it looks to be fairly untouched, for a while at least!
The missing valve is on the time base chassis PCB. Back bottom left corner. unfortunately there are no component numbers on the board so I have no valve number.
It looks as if the frame output valve and a sound output valve are on the same panel so I would guess this missing valve is the line oscillator.
Any help greatly appreciated!

Rich.
Edit. I think the chassis number is A481
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Last edited by slidertogrid; 7th Oct 2017 at 7:03 pm. Reason: added chassis number
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Old 7th Oct 2017, 7:20 pm   #2
ms660
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Default Re: Bush TV135RU missing valve ID

Line osc is shown as a PCF80 in a TV135R PTV article....Mag. page 65:

http://www.americanradiohistory.com/...on-1967-11.pdf

Lawrence.

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Old 7th Oct 2017, 7:58 pm   #3
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Default Re: Bush TV135RU missing valve ID

Many thanks Lawrence. I did a search for the model number and chassis number but I didn't find that article.
I'm off to find a PCF80!
Kind regards
Rich.
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Old 7th Oct 2017, 9:59 pm   #4
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Default Re: Bush TV135RU missing valve ID

First signs are encouraging, I fitted a PCF80 and powered up slowly. once I was happy the smoothers were OK I wound the voltage up to full mains. I got a faint line whistle but not a lot life otherwise. The brightness control and frame hold pots are broken so I will need to find replacements.
I found one of the boost capacitors missing and the other disconnected with the wire broken or snipped off the end of the capacitor.
I temporally lashed is a .22 capacitor and tried again. This time the line stage sounded much more lively and I was able to draw a good spark from the top cap of the DY87.
Playing around with the broken brightness pot gave me bright screen illumination or nothing. The frame transformer could be heard thumping away and the raster was flickering so I guess the frame speed is well out.
Switching to 625 produced a bright raster with some noise.
I then found I had no sound due to the speaker being disconnected.
Enough for tonight! I will see if I can find some replacement pots and try again tomorrow.

Rich.
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Old 8th Oct 2017, 7:36 am   #5
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Default Re: Bush TV135RU missing valve ID

Hello Rich,
That appears to be some fault tracing carried out just before it was 'scrapped'.

A single .1uf boost cap is OK. They originally used 2 X .1uf blue and white Dubiliar caps but this was changed to a single 1500V .1uf in the later A640 chassis.

The LOPT is prone to failure with a shorted turn overwind. Two types were employed, plastic [Plessey] and pitch,[RBM] both poor.

Other than that, Fairly straightforward and a good Mullard tube into the bargain.

Warning! There are many versions of the TV135 series. The early versions have a lot in common with the TV125U. Not one of RBM's best but they perform very well with a bit of TLC. John
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Old 8th Oct 2017, 10:37 am   #6
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Default Re: Bush TV135RU missing valve ID

A Murphy V929U (RBM TV135 R) was the first TV I brought back to life. The IF strip had low-gain, which was probably down to it having the original Hunts capacitors. I didn't know about how notorious they were back in 1984. The LOPT died very soon after, but I was able to get a replacement from Papworth Transformers.
I don't know if you could bake the moisture out of the over-wind in a old oven and dip it in something to seal the winding.

The good thing about the Bush 135 chassis is that where it has a VHF tuner it has valves in that too.
I re-labelled the buttons in mine for E2, R1 and E3 for TV-DX. I hacked the system switch to always give negative-going vision polarity but with the narrower band System A vision IF.
I also put potentiometers in a outboard case for AGC delay and line & frame frequency.
On one occasion I was playing around with the pincushion correction magnets using the old '0249' Soviet monoscope test pattern from the Soviet Union.It was from a Republic not often seen because it fell inside the usual distance for a single hop signal.
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Old 8th Oct 2017, 10:55 am   #7
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Default Re: Bush TV135RU missing valve ID

The fault I most remember about the 135R version with PCB sound, frame and line osc was the bad chassis connection under the self tapping screws, caused frame buzz on the sound. Cleaning the screws and PCB was a temporary fix, much better to add a wire soldered to PCB and chassis.

I didn’t have too many LOPTX problems with the Bush range of sets until the later models with the two large vertical PCB’s with the TX at the bottom of the cabinet between the PCB’s. Those did give me problems but straightforward to fix, easily completed in the house.
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Old 8th Oct 2017, 3:09 pm   #8
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Default Re: Bush TV135RU missing valve ID

Yes I realise there were various mix and match versions of this chassis. I have both the Bush and Murphy versions of the earlier sets with the plate glass screen. one later model also a Bush with a Transistorised IF PCB but still with Chassis timebase. This has a Panorama Tube without plate glass.
Then this set differs again same CRT as the later model but this time with a PCB valve IF and a PCB on the timebase chassis. This is the only one with UHF tuner fitted the others all have Dummy UHF buttons.
I found some suitable pots and this morning and replaced the Brightness pot, the 405 contrast pot and the frame hold pot.
With a bit of adjustment I had an upside down test card. swapping the frame plug around sorted that.
vertical linearity leaves a bit to be desired but the the positive side the tube is excellent and the lopt has held up so far..
Next is to try it with some signals on UHF and give it a bit longer run keeping an eye on the LOPT!
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Old 8th Oct 2017, 3:36 pm   #9
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Default Re: Bush TV135RU missing valve ID

The 135 with the transistor IF strip was for me very reliable compared to the 135R model. We installed the 135 and saw them 4 or 5 years later for and odd valve or some other component.The 135R was much less reliable.

If the CRT is good in your set that’s excellent, most the other problems will be fixable.
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Old 8th Oct 2017, 8:10 pm   #10
slidertogrid
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Default Re: Bush TV135RU missing valve ID

I have taken some pictures of the pot repairs and the pictures of it on the 405 test card. This evening I tried it on 625 from an old VCR. The 625 picture lacks the punch of the 405 picture but is still good.
The last picture of Columbo is on 625 it's not quite as grey as it appears. I had a bright light over the set when I took the picture.
Next job is to find some spade connectors for the speaker and see if I have any sound.
Rich.
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Old 8th Oct 2017, 8:16 pm   #11
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Default Re: Bush TV135RU missing valve ID

The pics of the broken pots are too big to upload. I replaced the broken/missing knobs keeping the original tracks. the knobs are not quite the same but are near enough..
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Old 8th Oct 2017, 8:25 pm   #12
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Default Re: Bush TV135RU missing valve ID

Excellent so far, those sets bring back some memories, I had just about started in the trade when the TV135's started to appear.

Lawrence.
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Old 9th Oct 2017, 8:39 am   #13
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Default Re: Bush TV135RU missing valve ID

That crisp 405 line picture was always a winner with my customers! Looks great. John.
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Old 9th Oct 2017, 8:55 am   #14
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Default Re: Bush TV135RU missing valve ID

We were selling the Pye range and RBM range of sets. Even after what I said about the R version not being as good as the transistor version they were still head and shoulders better than the Pye sets of that vintage.
Those integrated IF/Tuner sets from Pye/Ekco from the same era were terrible.

The Panorama CRT used in the 135 range did away with the safety glass, we still had many houses with coal fires and the static soon made the screen dirty. Favorite was the centre of the screen nice and clean with the corners black. The plastic mask got dirty as well. Try to explain the situation without embarrassing the customer, rest of the house spotless, just not the TV.

Most of our customers were really nice people, salt of the earth.
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