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HMV 2645 Thorn 1416 chassis

 
Mikey66
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This little (16") set appeared on (Facebook) marketplace search last Sunday afternoon. It was too close to ignore & the seller was only asking £20 for it.

Within an hour it was back at my place.

mc1
mc2
 
The set looked very clean with only a damaged on/off knob & a missing bright from the brightness control. Inside it looks untouched with no obvious signs of any repair work.
 
mc3
mc4
mc5
 
Tonight I got the chance to investigate it further. Some kind soul had chopped the mains cable down to a 6 inch stub, but I managed to get it wired into my speed block.  really don't like loud bangs so I snipped the mains filter cap, C101.
 
Power was applied..... and nothing, no heaters, no smoke. A poke around showed mains fuse was dud, Ah, there was another fuse taped to the back of the set, but that one was dud too. A search for 1.5A 320mm fuse ensued. The nearest value I had in the size is 1A so that was tried. The new fuse blew as soon as I powered the set up again. Time to get the circuit out. I found it in a December 1969 copy of Television, part of an excellent servicing article by LLJ. W11, the HT rectifier, was the culprit, with a new diode & fuse fitted the set was powered on again. This time I propped the chassis open so I could get a better view of any prospective smoke bombs.
 
After a few seconds I had a nice bright, snowy raster. I was just about to plug in a test pattern when the magic smoke appeared from the bottom left of the chassis. After removing the mains I probed around the area with my finger, C81 (12uf) was hot to touch and once removed showed signs of leakage. It's one of those lovely Callins capacitors Thorn were so fond of back then.
 
A replacement cap was fitted and the set powered up again. I managed to tune it in to my pattern generator and was about to photograph the picture when line lock disappeared  and the image shrunk to a 1 inch wide vertical line. At his point I switched off and decided that's enough for tonight.
 
So far the component tally is thus..

PXL_20210210_205843941.jpg
 
To be continued....
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Topic starter Posted : 10/02/2021 10:41 pm
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Cathovisor
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Looks quite a respectable little set there. I can almost smell those PCBs when you soldered them.

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Posted : 10/02/2021 11:39 pm
RichardFromMarple
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Looks like a nice little set, here's link to a picture of brochure page of one:

 

 

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Posted : 11/02/2021 12:05 am
colourstar
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That's a very attractive little set and in great condition too by the look of things. I'll keep my eyes peeled for a correct knob as I'm visiting a friend's tv graveyard next week. It sounds like your set wants to live. I reckon you'll have it up and running for the weekend. Best of luck!

 

Steve

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Posted : 11/02/2021 3:36 pm
Mikey66
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@richardfrommarple

 

Hi Richard, the set came with the HMV sales brochure and price list  from February 1969

HMV 2.jpg
 
HMV 1.jpg
 
I'll have another look at this set over the weekend
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Topic starter Posted : 11/02/2021 9:28 pm
Mikey66
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Just a quick question about the valve line up in this set.

All the valves bar the PCL805, PY801 & PL504 are Mazda branded.

The PL504 is a Mullard - possibly a replacement?

The other 2 are branded "HRS AG" I've never heard of them before.

PXL_20210211_205829727.jpg
 
PXL_20210211_205849062~2.jpg
 
Would these have been fitted at the factory?
 
Mike
 
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Topic starter Posted : 11/02/2021 10:36 pm
Nuvistor
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@mikey66

The Mullard is  probably a replacement, HRS were if memory serves me right a wholesaler for radio and TV spares, they may have done white good spares as well. I don’t think I used them but you never know I could have had the odd item that wasn’t available easily from other suppliers.

I don’t remember what the HRS stood for, the AG part of the name, do German companies use that suffix? I didn’t see HRS AG on any parts.

Snippet from Sept 1977 PT

9170BCDB CEDD 422B BB0E 0FC636CCF865

 

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Posted : 11/02/2021 11:26 pm
Cathovisor
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Posted by: @nuvistor

I don’t remember what the HRS stood for, the AG part of the name, do German companies use that suffix? I didn’t see HRS AG on any parts.

Snippet from Sept 1977 PT

9170BCDB CEDD 422B BB0E 0FC636CCF865

 

AG = Aktiengesellschaft = Corporation.

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Posted : 11/02/2021 11:56 pm
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Katie Bush
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I have exactly this set! Mine works well, but does need those Callins caps replacing. The caption buzz on these Thorn 1400 chassis is something wicked, but since mine was and will be used mostly on 405 lines, it's no a big issue. There were a lot of suggested mods in "Television" but I never came across one that actually cure it. One actually made it worse!

Funnily enough, mine was missing a knob when I bought it too!

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Posted : 12/02/2021 5:51 pm
jjl
 jjl
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The junior school I attended between '72 and '76 had several of these sets. I had to move one of them once - it was heavier than I thought it would be.

 

John

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Posted : 14/02/2021 12:47 pm
Katie Bush
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Another point worth noting. . . Those Callins caps, if not dealt with, can destroy your audio output transformer, so the better on hoicking them out! - There are two, if I recall, and the only two Callins in the entire set, if memory serves me?

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Posted : 14/02/2021 8:52 pm
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malcscott
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It might be worth checking the heater rectifier diode.

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Posted : 15/02/2021 2:32 pm
Mikey66
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Hi all. Work has stopped on this set until a new 30FL1 arrives (hopefully this week).

Checking the line drive on the PL504 and it was varying between -60 & -5 volts. Cold checks on the line oscillator/driver components threw up nothing obvious.

Fingers crossed the  30FL1 is the culprit. Though closer inspection shows previous repair work around the line driver transformer.

I'll change the heater diode and that other Callins cap in due course 👍 

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Topic starter Posted : 16/02/2021 8:51 am
Mikey66
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Another update on this set.

A new 30FL1 arrived and was fitted...no difference.

The fault was still there, erratic line hold and loss of line drive after a couple of minutes.

More cold checks and following Marion's advice about the other Callins cap. This was C52, the HT reservoir for the line driver / oscillator stage.

C52 was obviously distressed but it had also taken the HT feed resistor R66 with it. R66 measured nearly 60kΩ (should be 4.7kΩ).

I really should be more thorough when I'm doing cold checks.

TCE 1416 1

 

Replacing these two and refitting the original 30FL1 got the set working with solid line lock.

TCE 1416 2

 

Whilst the set now displays a picture I need to sort out the sticky system switch and the issue of the sound and vision not tuning in correctly.

Via my freeview box I cannot resolve a picture and sound together - it's one or the other. I'm hoping the phantom twiddler hasn't been in there 😮 

 

PS. Does the offer of a spare knob still stand Chris?

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Topic starter Posted : 19/02/2021 7:58 pm
crustytv
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Posted by: @mikey66

PS. Does the offer of a spare knob still stand Chris?

Absolutely Mike, but you'll have to refresh my mind on the type and measurements. I know I have them as I've supplied two other members, but it was years ago. Since then, I've amassed a lot of knobs, having measurements and a good, clear photo will help me narrow it down when I go rummaging.

20210219 202402
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Posted : 19/02/2021 9:30 pm
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Mikey66
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Crikey! That's a lot of knobs 👍 

Thanks Chris, I'll PM you some dimensions & photos later this weekend.

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Topic starter Posted : 20/02/2021 10:40 am