HMV 1124 - Has Been Tested And........

[Murphyv310]

I'm rather puzzled by the recent post from NM which starts:

Terry wrote this I think further back:

"Having no idea of the age of the set, the connection between the smoothing and the reservoir sections of the smoothing can may be either a resistor or a choke, and I would guess that this is where the problem lies."

You were on the right track over the high voltage but it wasn't the resistor ...

After detailing his progress after this he continues:

... now for the less palatable bit:

I do not personally engage in the use of emotive or patronising language directed at other members on websites. I also dislike the current trend where people who are connected to engineering seem to be exhibiting excessive and pointless ego ...

which seems to imply that my advice is the target of this unwarranted attack.

Mark, in his reply to this says that "I'm satisfied that he isn't deliberately setting out to offend "  but that doesn't seem to be the case from where I'm standing ...

Hi Terry.
I have felt too that NM has got just a little too close to the bone.
For an amateur he displays a very arrogant attitude, I wonder if he takes in the good advice shown here.
Why he should say those connected to engineering have excessive and pointless ego beats me!
My answer to that comment is NM may just have burned his bridges!

[Mark Hennessy]

I'm rather puzzled by the recent post from NM which starts:

Terry wrote this I think further back:

"Having no idea of the age of the set, the connection between the smoothing and the reservoir sections of the smoothing can may be either a resistor or a choke, and I would guess that this is where the problem lies."

You were on the right track over the high voltage but it wasn't the resistor ...

After detailing his progress after this he continues:

... now for the less palatable bit:

I do not personally engage in the use of emotive or patronising language directed at other members on websites. I also dislike the current trend where people who are connected to engineering seem to be exhibiting excessive and pointless ego ...

which seems to imply that my advice is the target of this unwarranted attack.

Mark, in his reply to this says that "I'm satisfied that he isn't deliberately setting out to offend "  but that doesn't seem to be the case from where I'm standing ...

Well, I'm equally puzzled by your post. Why resurrect this some 2 and a half weeks after I attempted to smooth over things? Things have moved on since then...

The simple fact is that NM has a different way of communicating with us, in part thanks to his limited access to the internet. That has led to many of us - myself included in the past - to become frustrated with him, and that has been apparent in many of our posts. NM could have justifiably taken offence at a much earlier point, but the post you quote is - to his credit - the first time he has allowed his frustration to surface.

Yes, I accept that there are one or two aspects of that particular post which we could latch on to, but taken in the round, I decided that it was best to call it quits and move on. I think my earlier post did that pretty well.

Ultimately, tolerance and respect are the basic requirements of membership here. It's not always easy - and I've admitted my own shortcomings already - but we must try. I'm not asking for anyone to give NM special treatment - and I'm certainly not. NM is subject to the same rules as the rest of us.

Just so everyone knows, I'm going through an especially busy time at the moment - as is usual for this time of the year - so I'm not posting as much as normal. However, I am checking in frequently, and I am reading every post that is made on the forum. That said, if you need a quick response, please remember that you can report problematic posts - or you can send a PM or email to myself or anyone on the team.

Does this help?

Mark

[Nowhere-Man]

I'm rather puzzled by the recent post from NM which starts:

Terry wrote this I think further back:

"Having no idea of the age of the set, the connection between the smoothing and the reservoir sections of the smoothing can may be either a resistor or a choke, and I would guess that this is where the problem lies."

You were on the right track over the high voltage but it wasn't the resistor ...

After detailing his progress after this he continues:

... now for the less palatable bit:

I do not personally engage in the use of emotive or patronising language directed at other members on websites. I also dislike the current trend where people who are connected to engineering seem to be exhibiting excessive and pointless ego ...

which seems to imply that my advice is the target of this unwarranted attack.

Mark, in his reply to this says that "I'm satisfied that he isn't deliberately setting out to offend "  but that doesn't seem to be the case from where I'm standing ...

Hi Terry.
I have felt too that NM has got just a little too close to the bone.
For an amateur he displays a very arrogant attitude, I wonder if he takes in the good advice shown here.
Why he should say those connected to engineering have excessive and pointless ego beats me!
My answer to that comment is NM may just have burned his bridges!

Hmmmmm, I've been working pretty hard on that HMV over the weekend and I log on to post a few comments about this onging work and I find the atmosphere is somewhat sour.

Yes, it is true there has never been any intention to offend. The same applies to Terry's post. On the contrary, that had been quoted earlier because I'd actually thought Terry's observation had been a good one.

The stuff I posted about ego before was really based on experience on another website and not really related to here. True, this thread had been getting a bit heated earlier on but I think I was trying to say let's keep it friendly. One way to do this maybe just to PM me in case of any misunderstanding? That might help to keep the atmosphere relaxed and friendly.

Personally speaking when I log on, it's often a case of just wanting to unwind a bit and not get overly serious. I find the radio work hard going as it is and so a sense of humour can iron over many wrinkles.

[Nowhere-Man]

Back to business:

The anode voltage on my KT61 checked out better that I'd thought. It seemed reasonably on spec. Having said that, I may attempt to change an AF coupling cap on the grid of the DH77 which it seems hasn't yet been replaced. Physically it looks a bit shoddy and tired. Where it gets difficult is the tube bases on this set are amazingly cramped. Just to get at the grid with a soldering iron from below may be a headache. I don't know why they cramped the bases to the extent it was done but I suppose there was no concept of the AF cap needing to be replaced within 20 years!

I did test the AVG diode load of the W77 and this was also very tricky as the leads of the resistors are too aged to make good electrical contact with the meter. I had to scrape a lot with a blade. I think it's at one Meg.

The AF coupling to the grid is shown on the schematic as a variable resistor with a variable resistance on the grid via the capacitor which I think is 0.02 mF. I'd be happy if I can snip this out and solder in a brand new capacitor.

I also replaced and repaired the aerial wire. The pin had been found to be bent and the aerial wire itself had lost most of its insulation. It was wise to deal with this in the event of a short while testing.

The radio seems to work O.K. in its limited way. It seems more "bedded in" but I now have the job of testing all the specs from the output valve downwards.

[pwdrive]

Yes, measure all the valve voltages and make a mental note of what they are in proportion to each other, anything you are not sure off then post a question on this forum, familiarity and what to expect is one of the key aspects to understanding all this stuff about radio's etc, the more you do the easier it becomes from a fault finding point of view.

Keep at it.

Lawrence.

[Nowhere-Man]

Here is a pic that hopefully gives some idea of the circuit mounting. The red capacitors are mine. I use these as they're probably a fair bit cheaper to buy than stuff you'd get on specialist sites. It means for a few pence I can replace a lot of knackered wax capacitors.

This pic gives the best illustration of "The Rail" so far. The Rail appears to be the whole axis of the radio design - a means of neatly tucking away all those bypass capacitors so they don't intrude. Apart from soldering, the components were twisted into place to make a very secure connection.

As you can see, this led to a great deal of repair problems. Removal of the entire rail to create access carried quite a few risks. So easy for something to either get mixed up or even accidental breaks of a circuit connections. Part of this rail is soldered onto chassis or tube pins as well. In the end, I decided to take an easier way around it and try and solder around the rail. You can see the black leads where this was done - it had to be wire that was a bit rigid so it would support the film cap that was replacing the old wax. Needless to say, most of the wax caps were so degraded and dirty they had to be snipped out and chemically cleaned to reveal the rating, typically 0.05 or similar.

At any rate, I take the view this was just a very bad design idea by the manufacturer. It restricted access to most of the tube bases. It made it very awkward to work on the radio and actually trace the circuit. It involves soldering in very awkward spots and enough to try the patience of the Prophet Job. A good deal of this work was done cursing and cussing.

[Nowhere-Man]

There has been a real mystery that involves the AF grid coupling to the DH77 grid. It was a minor point so far as the overall picture is concerned but I decided to start from the output tube stages and onwards till I get to the Mixer stage.

The mystery came to be when I was carefully testing the DH77 grid bias. According to the manual I think it's R9 which builds up a D.C. voltage in the volume stage (R9 being the potentiometer resistance up to 500 K.) According to Chas Miller, this should always be checked since he found over time many repairers had been using 5 K pots by mistake. Mine was a new unit just shy of 500 K but I wanted to make sure I could trace the variable resistance to the grid, while moving the volume shaft. Of course, as is known, you find it's pretty close to zero in the near-off position and, at full volume, it goes up to 500 K.

So, I notice a small and worn-looking capacitor that goes directly to the grid of the DH77. Well, I looked at the schematic and at first I thought it had to be the AF coupling cap. Now, I'm not so sure at all. There is in fact a Sprague cap that goes to the same grid via the other shoddy cap. The former also looks far more like a picofarad capacitor due to being a fair bit smaller than the bypass caps I removed. The latter is rated accordingly for the AF coupling. So, I tested the variable resistance across the Sprague and this naturally is in circuit with any bias on the grid. Conclusion? There is no way to get access with the soldering iron direct to the grid so I left well alone. Just have to wonder whether there is some sort of a filter cap that's been left out of the circuit diagram or did they use 2 caps to make up a total value??

Circuits diagrams can be tricky I find in cases where a tube pin connects to chassis. In reality you see a resistor that seems to emerge from a pin but in the schematic it only shows as a remote connection to chassis and far removed from any tube.

Anode voltage on the output tube seems fine.

I already have suspicions my Mixer Tube is underperforming but that will remain to be seen...

[Nowhere-Man]

UPDATE:

Something strange happened today when testing voltage around the X78 Frequency Changer. Like most of the tube bases under the chassis, this was tricky to get at. In such circumstances I tend to tape the red probe of the meter so only the very tip is conductive. This avoids any accidental bridging of voltages in cramped areas. I was seeking out the Triode Hexode H.T. anode and, on finally locating it, the voltage showed up on the meter. This was on spec. However, the signal strength improved dramatically and I was getting really good sound. Speaker volume shot up and tone improved. On removing the probe, volume would drop and audio output would be not as good. Could this be a result of the load on the anode or was conductivity simply improved? I'll investigate.

All testing so far indicates the output stage and power supply stage aren't so bad at all. I suspect the areas I need to look at more closely are the Mixer/Oscillator part of the circuit.

It should be noted the tube bases are "rickety". I cleaned up the pins and it would be nice to re-solder some base wires with new wire if I can get access.

[Refugee]

I would try adjusting the aerial trimmer.
It should be shown on the circuit diagram and may be accessible from the rear of the chassis for adjustment during installation of the set.

[Terry]

The  Triode & Hexode are two completely separate valves, although interconnected and in the same bottle.

You don't say which anode you were checking but I assume it was the Hexode because touching anything in the local oscillator (Triode) section would have sent it way off tune!

The result you got suggests that the alignment of the aerial input circuit is badly out. Assuming the use of a decent aerial, I wouldn't normally expect to get this sort of improvement.

I thoroughly sympathise with the problems you are experiencing with test prods. There seems to be a trend these day to supply prods with very long uninsulated ends which have to be carefully held in place.

RS used to do a neat sprung probe which looked very much like this:

http://www.ebay.co.uk/itm/90-Banana-Plug...1243831883

They aren't very long, so you'll need a different pair for extended reach but they are ideal otherwise. If they are the same as the ones I remember, the centre wire is bent over at the end to form a hook. As seen in the picture, only the very end of the probe makes contact with anything but, by pressing the knob at the other end, the probe should extend and turn into a sprung hook about 3mm long which clips on the measuring point when you release the button, leaving you with both hands free.

The RS one was operated by sliding the sprung insulator with the thumb, which would probably be easier to use so, if anyone has got some 50 year old RS sprung probes they don't want, can I have first dibs, please?