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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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14th Nov 2014, 11:23 am | #61 | |
Dekatron
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Re: Murphy V180 restoration.
Quote:
So, the first stage of the repair I must concentrate my attention to the left side panel first. A perfect 90 degree angle is required at the top left side edge in order to set a reference for the remainder of the cabinet reconstruction. Pictures to follow. DFWB |
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14th Nov 2014, 4:57 pm | #62 |
Dekatron
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Re: Murphy V180 restoration.
In order to make good the upper left corner of the cabinet a new corner block has been made and fitted in place. As you can see from the attached picture it has been glued, screwed and clamped in position.
The next stage of the straightening up process will be to deal with the other side. This might involve removing the cabinet floor first. Also,the batten that supports the front castors needs replacing, it's warped. DFWB. |
14th Nov 2014, 5:31 pm | #63 |
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Re: Murphy V180 restoration.
That's more like it. A perfect right angle.
DFWB. |
14th Nov 2014, 6:50 pm | #64 |
Octode
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Re: Murphy V180 restoration.
Looking much better, should be fairly rigid now.
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14th Nov 2014, 7:25 pm | #65 |
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Re: Murphy V180 restoration.
Hi Steven,
It certainly is. The top right side corner has now received attention from my instruments of torture. It's a just as well that this is not a chargeable restoration job. Imagine the bill for all this work? DFWB. |
15th Nov 2014, 9:56 am | #66 |
Octode
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Re: Murphy V180 restoration.
Well done David, excellent work.
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15th Nov 2014, 9:55 pm | #67 |
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Re: Murphy V180 restoration.
The batten which carries the front castors was warped and so todays work involved making and fitting a new part.
Replacing the front batten has further helped to stiffen up the cabinet. It is becoming a very rigid structure. DFWB. |
17th Nov 2014, 10:03 pm | #68 |
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Re: Murphy V180 restoration.
Although the cabinet is much better than it was, it is still slightly twisted out of shape. This left me only one more alternative other than replacing that warped right side panel. A diagonal brace has been made and fitted at the bottom of the cabinet. See the picture. The brace ensures that the left side panel will not be pulled inwards again when the deformed right side panel is screwed and glued into position. So to sum up, the left side panel is now rigid and so it is the right side panel that is pulled back into it's correct shape after the floor and the lower rear batten which carries the castors is reattached again.
DFWB. |
17th Nov 2014, 10:14 pm | #69 |
Octode
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Re: Murphy V180 restoration.
Time to put the saw, chisel and glue away and get the soldering iron up to temperature
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17th Nov 2014, 10:39 pm | #70 |
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Re: Murphy V180 restoration.
Hi Steven,
That's right, although the line output transformer is away for rewinding a fair number of capacitors have been chosen for replacement. For example, all those waxies in the frame timebase. Also, although the line timebase is out of action it is still possible to test the vision and sound stages. DFWB. |
22nd Dec 2014, 11:17 pm | #71 |
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Re: Murphy V180 restoration.
Update on the progress of the restoration of the Murphy V180C.
The cabinet has been prepped up for the final part of the re-finishing job. The sides are painted black and a detail of this colour extends around the edges of the cabinet top. Note the repair work that has been carried out along the right top side and the rear edge. The colour of the repair veneers does not matter here because of that black detail. It extends inwards about an inch. The cabinet is now really solid, no longer the flexible thing it once was. DFWB. |
6th Jul 2015, 9:14 pm | #72 |
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Re: Murphy V180 restoration.
Latest news. The rewound line output transformer has been fitted and the set is tested without the CRT. There is a now healthy flame like spark present at the anode of the U24 EHT rectifier.
The original boost diode was a Mazda U281, this valve has been replaced by an U301, see post #40. Although I have found another Mazda U281 the replacement valve will remain in place. The next task is to re-fit the CRT. DFWB. Last edited by FERNSEH; 6th Jul 2015 at 9:23 pm. |
8th Jul 2015, 9:33 pm | #73 |
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Re: Murphy V180 restoration.
This is going to be one cracking set once complete. Excellent work thus far.
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9th Jul 2015, 11:53 am | #74 |
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Re: Murphy V180 restoration.
The CRT was refitted today, it is displaying a very bright raster but no pictures. This is a Holme Moss channel 2 receiver, it should be a simple enough task to tune the set to channel B1.
Some sets employed the Mazda 6C9 for the frequency changer, this later production set uses a Mullard ECH42 instead. DFWB. |
10th Jul 2015, 8:43 pm | #75 |
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Re: Murphy V180 restoration.
You'll recall that John HKS experienced problems with his Murphy V114 in the vision IF amplifier, well it turns out that my set has also a problem in the same part of the circuit.
When the contrast control is advanced to maximum the screen suddenly becomes bright. The fault has been traced to the first vision IF amplifier stage. Short circuit the grid of the valve to chassis and the oscillation stops. The decoupling capacitors have been checked and they are OK. DFWB. |
11th Jul 2015, 9:05 pm | #76 |
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Re: Murphy V180 restoration.
I decided to tough this one out this afternoon.
The source of the oscillation has been found, it was in the sound IF amplifier! The 0.003microfarad screen grid decoupling capacitor of the sound IF amplifier valve had gone OC. The oscillation present between the grid and cathode of V8 had found it's way through the coupling transformers into the vision IF amplifier. The V180C has two RF amplifiers before the frequency changer, V1 and V2, both Mazda 6F12 pentodes. The first RF stage is in a small sub assembly and is attached to the upper part of the signals chassis. There is a fault in this unit because no signals are passing into the main chassis . When the signal generator is connected to the grid of the second RF stage modulation is present across the vision detector load resistor. Rest assured the restoration of the is set is by means not finished yet. the frame timebase needs sorting out next. DFWB. |
12th Jul 2015, 12:17 pm | #77 |
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Re: Murphy V180 restoration.
At last signals are coming though from the aerial socket to the grid of the CRT.
The first RF amplifier was in fact OK, so why was it only possible to inject signals into the second RF stage? The reason for this turned be a fault in the second RF amplifier, the screen grid decoupling capacitor of V2 was OC so it is likely the amplifier was oscillating at some indeterminate frequency. When the lead from the signal generator was connected to the grid of V2 the oscillations were damped and signals were allowed to pass though. All the faulty capacitors were Hunts make and there is plenty more of that make in this set so it would be wise to replace all of them. DFWB. |
13th Jul 2015, 12:17 pm | #78 |
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Re: Murphy V180 restoration.
'Scope trace of the video present at the grid of the CRT. 50 volts of positive going video is available before clipping starts after the contrast control is advanced further.
DFWB. |
14th Jul 2015, 11:25 am | #79 |
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Re: Murphy V180 restoration.
It is pretty obvious there is quite a lot more work to do to this set. The frame linearity is still not right even after replacing all the waxies. There is one more capacitor to check in the frame timebase, an 8 microfarad electrolytic which is connected between the screen grid of the 6P25 to it's cathode.
DFWB. |
14th Jul 2015, 11:57 am | #80 |
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Re: Murphy V180 restoration.
I wish my BT8161 WFM looked as good as yours, Fernseh!
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