Hi all,

I bought an HMV "Rangemaster" console model on eBay recently, and I'd greatly appreciate any info there is on this. It uses a vertical chassis with the EHT cage in to top right corner. I have a schematic for the M1 chassis, but mine is slightly different, I notice the yoke plug terminations are not the same, and my yoke doesn't have any capacitors. Unfortunately, it doesn't have a decent plastic locating cap either: it's falling apart! (Anybody have one for sale?)

I measure HT1 and HT2 ok, but the boost volts are way too low (yoke disconnected, but wire interlock connected in place) and I'm fairly sure the flyback transformer isn't operating. I'm not sure if the yoke needs to be in place for this to happen, but with it connected, the HT rails drop significantly and I can hear a hum that suggests that the power transformer is being stressed. (FS3 blew at one point) I've also left off the final anode cap to the tube so I don't burn the phosphor should I get a result. I have replaced all the electros and wax caps.

Any info that somebody has or a point in the right direction would be greatly appreciated, as this TV would be great to restore. Luckily, I can get a sound signal when I touch one of the aerial pins, so it's "just" the picture I need to sort out. I used to work on these as a kid, but of course never had much luck if the fault was more than just valve swapping.

By the way, there was a (poor) image on the tube in one of the eBay pics, so I've probably stuffed something up when I recapped it, or I now have a shorted yoke. My suspicion is my recapping, though.

The model I have is PJ-A7.

Cheers,

Adam

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"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

Hi Adam,

Good to see you're having a go at getting your HMV going. For starters, the M1 schematic while similar has several differences to your PJ chassis so you may have introduced a wiring mistake if you followed it.
I don't think I can upload the schematic onto the forums due to its size but if you unhide your email address in your profile I can send you a copy.

The reason your boost volts are low is because you have disconnected the yoke. The deflection coils are a critical part of the horizontal output circuit and it won't function correctly without it. Thats the reason for the wire interlock - to prevent what you are trying to do.
Since you have said that you are experiencing a large drop in HT with the coils connected there may be an issue elsewhere that needs addressing first. My advice for fault finding at this stage is to disable the the deflection circuits by unplugging the yoke (and don't bypass the interlock) and confirming that the voltages and currents are correct for the rest of the circuits. Once happy with that, reconnect the yoke and recheck the voltages.

If FS3 blew that indicates a fault somewhere other than the deflection circuits as it feeds the small signal circuits.

One last thought, if the horizontal oscillator is not running the Horizontal Output valve will be operating with no bias and will overload the power supply. This may be what you are experiencing but more fault finding needs to occur first.

To do a rough check on the oscillator measure the voltage on the grid (pin 5) of the Horizontal Output valve, it should be around -30 to -40 volts with respect to chassis. (Note this is a NEGATIVE voltage!)

Andrew

Andrew, if you are able to e-mail me the image I can reduce it to size without a loss of clarity and upload, and perhaps link to a hosted copy of the image in original size.

My mail server has no restrictions on the size of mail received.

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A valve a day keeps the transistor away...

Thanks Brad, I've emailed you the schematic. Having it here will make things much easier when discussing the circuit.

Hi guys,

thanks a lot for the help, I have set my email address to show...I thought it was on by default.

I would very much appreciate the cct diag, (as large as poss file size) becuase I think I stuffed something when I recapped it. The seller on eBay had taken a shot of the TV showing a poor raster pattern. I asked if it was a recent pic as I didn't want to plug it in unless it was.

At the time of recapping, I just took out one cap at a time and replaced it lead for lead, but I probably soldered one of them in the wrong place. I've definitely seen differences in my TV with the M1 chassis, I'm guessing mine is a newer version. Ultimately I'd like to get one with the more rounded tubes.

Thanks also for the tip about boost volts, I suspected that the yoke needed to be fitted in order for the flyback transformer to operate properly. Most of the pins are currently hovering around the HT rail voltage, and I guessed that there's something important missing! Even with the yoke fitted, I still get no high voltages, but I suspect as you're saying, the problem is further back.

I'll also check the horizontal osc, easy enough to do.

Thanks again for your input, really appreciated. I have been wanting to tackle a challenge like this for ages... the Jaycar kits just don't cut it any more!

Cheers,

Adam

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"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

Click on the circuit diagram to access the full size version. Warning - it is a very big file, just over 2MB.

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A valve a day keeps the transistor away...

Thanks so much Brad and Andrew, for your excellent quality schematic. Are there any voltages or waveforms available anywhere?

There certainly are differences in the horizontal section to the M1. This cct diag you've posted matches what I'm seeing on my chassis perfectly, it'll make it so much easier to troubleshoot now. I also now know what the slider pot in my TV does now...focus!

BTW if anyone wants the M1 diag, please let me know.

I'm using high voltage "greencaps" instead of the waxies... is this OK? I've had no bangs or smoke etc., but any advice in terms of whether the properties of these caps are suitable or not would be useful. Jaycar's range (which is what I've used) is quite limited in the high voltage stuff, Speedy Spares are better, or Farnell I'm thinking if nothing else.

All help appreciated!

Adam

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"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

The PK chassis dates from around 1962-3 while the earlier M1 chassis is from around 1959.

High voltage greencaps are fine for use in all parts of the circuit to replace wax capacitors providing they have an equal or higher voltage rating than the parts they have replaced.
Some of the capacitors you have replaced had 1000v ratings, have you been able to get suitable replacements?

I do have the waveforms for the circuit. Do you have access to an oscilloscope? If so that will make troubleshooting much easier.

Here are some of the key voltages you need. Unless noted otherwise they refer to valve number then pin number.

HT1 (Junction C50 and R46) 238v
HT2 (After FS3) 203v

V12 pin 1 150v
V12 pin 3 and 8 7.2v
V12 pin 6 117v
V12 pin 7 -7v

V13 pin 4 168v
V13 pin 5 -37v
V13 Top Cap DO NOT MEASURE

V15 pin 9 238v
V15 Top Cap DO NOT MEASURE

B+ Volts (Junction C118 and C119) 780v

There are two variations of horizontal output circuit. One uses Philips parts and the other uses MSP parts. The diagram I've uploaded shows the Philips type. You can tell if you're TV uses the Philips parts by confirming the colours on the Yoke plug match those on the diagram (shown just left of the power transformer).

Hope this all helps,

Andrew

Hi Andrew,

thanks again for your wonderful info. Regarding the 1000V caps, I used 2 630V caps in series of the approx value to get what I needed. Jaycar's range is a bit limited, so I had limited options.

I'll check the yoke wires when I have some spare time and see what version I have. I don't have a CRO unfortunately, I sold mine years ago when I stopped work on colour TVs, but I may get another. This is my first project in restoration. Probably won't be my last though, I'd prefer the older M1 and I'd like to get hold of an AWA Radiola.

I hear you loud and clear about the anodes of V13 and V15! I remember the arcs that I used to be able to get from these as a kid, luckily I'm still here. I'm not getting an arcs at at the moment though, no surprise there.

I've cleaned up the cct diag you posted in photoshop, I'm happy to post it back if you like or email it to you. Still not brilliant, but I have a bit more work still.

I'll keep you posted and thanks again so much for your help, I wouldn't have had a chance without the right diag.


Cheers,

Adam

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"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

Glad to help. I'll be interested to hear how you progress.

I'll keep you posted! Hopefully I'll have some time to look at it this weekend. I'll print out and laminate the cct diag and finally have something useful to work with.

Cheers,

Adam

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"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

WORKING!

Thanks a lot guys, your info was exactly what I needed to get my baby up and running. I had made a mistake as I suspected when recapping. There is a shielded lead that comes from pin one of the 6U8 that leads on to pin 6 of the flyback then on to the yoke socket.

When replacing cap C120, it was difficult to see exactly where this went on the yoke socket side of things, and I had also connected the earthed braid from said shielded cable. (should have been floating) Turns out I was causing a short which is why I was hearing a hum every time the yoke was connected properly and the voltages were way down.

I had followed Andrews supplied voltages and found them to be correct until the yoke was connected. A quick check of the schematic against what I could see on the chassis showed my mistake. I NEVER would have picked this without the diagram! (Lucky I didn't kill the set with my short, I never ran it for long in this condition for fear of burning out the mains transformer.)

And that was the last capacitor I replaced, too! I now have a raster, a watchable pic (when I touch one of the aerial terminals) and sound which has always been OK.

I think I'll have to fabricate a new yoke cap, as the pic is torn away on the top corners and can be improved greatly if I gently move the yoke rings which are only just being held loosely in place.

I'd post a pic on the forum but I'm not sure how!

But thanks again everyone, I really couldn't have done this without you and now I have a lovely piece of working furniture. I few minor adjustments after the yoke ring issue sorted and I think it'll be perfect. The tube is nice and bright.

Cheers,


Adam

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"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

Well done on getting it going, I didn't think it would have been too big a problem considering the TV was working when you got it.

The rings on the back of the yoke are picture centering rings. They are slightly magnetic and are adjusted to make the picture central on the face of the picture tube. They are not particularly critical as long as they are held in place. You should be able to arrange something to hold them in place.

To post pictures of your TV you can email them to Brad. Click on his name in the post earlier on to see his contact details.

Hi all,

I've just sent the pics to Brad. The Yoke socket closeup shows my mistake with the shielded cable.

I'm trying to fabricate some sort of yoke cap out of odds and ends, I'll post pics of that too. A Dremel is very useful for these small parts. A mate in the UK is working with a fibreglass option, which will probably be better than mine!

By the way, does anyone have one of those really cool Predicta TVs?

Cheers,

Adam

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"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

The Philco Predicta TV's were only sold in the United States (I think) so there won't be any in Australia unless it was a private import.