[morzh]

Steve,

Before you proceed, do check tubes, check transformer with rectifier tube removed, check tubes, especially rectifiers, electrolytics polarity, and short after rectifier and across all filaments.

[kiwi_steve]

Steve,

Before you proceed, do check tubes, check transformer with rectifier tube removed, check tubes,  especially rectifiers, electrolytics polarity, and short after rectifier and across all filaments.

Great advice   Tubes are all new and tested (the old tubes were only half present, and I'm not re-using the 36 or the 6-series tube someone had installed in place of the 75 so I needed to get new ones for those and the missing ones - and I got a good deal on a complete set).  The original rectifier (80) tested ok in my tester - but its not the most reliable piece of equipment I own... and the transformer tested ok on the bench - but it has yet to have power through it.  I avoided testing it because this way I will be motivated to rewind (or have it rewound) if it needs it.  There was a lot of wax around the wiring so its been warm in the past... We will see...

You've just made me second-guess myself about the electrolytics... I may pull them out now to double check

And checking for a short on the filaments is a good idea... I'll do that too since I'm reusing the original wire and it runs all along the chassis edge.

[GarySP]

Welcome to the phorum, Steve.  Your neck of the woods is on my bucket list to visit...someday.  In answer to your much earlier question about converting to a three wire line cord, yes, with this set you can connect the ground to chassis.  This is evident in your photo by the riveted ground clip on the back of the chassis to the right of the insulated antenna clip.  This is not always the case, but since it was intended to have a ground wire to earth you are really not changing anything.  The only possible disadvantage is that by grounding to the home wiring you could pick up "noise" from other equipment and appliances tied into the same ground network.  Take care, Gary

[kiwi_steve]

Your neck of the woods is on my bucket list to visit...someday

Thanks Gary - your neck of the woods is on mine too - although I'm pretty sure I'm going to need my own UPS plane to get home with because there are so many amazing radios I see in YouTube videos of swap meets and the like over there that I'm bound to want to buy a pile of them... not to mention test gear - VTVM's, valve testers and the like hardly seem to come up here - but I see them on eBay all the time in the US for cheap-as-chips... If I do come over - I will definitely co-ordinate it with some kind of vintage radio swap meets so I can not only see what will fit in my suitcases but hopefully meet a few people and talk valves (thats tubes for you guys) over a beer or two as well.

No progress on the radio last night... late nights caught up with me... it might be the weekend before I get back into it now due to other commitments... we'll see... it seems so close now (if you don't suddenly remember the state of the cabinet I have yet to touch, or the speaker which I have not yet even tested)

In answer to your much earlier question about converting to a three wire line cord, yes, with this set you can connect the ground to chassis.  This is evident in your photo by the riveted ground clip on the back of the chassis to the right of the insulated antenna clip.  This is not always the case, but since it was intended to have a ground wire to earth you are really not changing anything.  The only possible disadvantage is that by grounding to the home wiring you could pick up "noise" from other equipment and appliances tied into the same ground network.  

Thanks for the reassurance regarding the earth connection.  The only thing I'm likely to get interference wise is the fluro light in the radio shack and the electric fence which provides a somewhat annoying static-crackle metronome in the background of all my radios (but its a small price to pay for not living in the middle of a city).  The worst noise was when I converted some of the lighting to LED.  I've got 1m (about 3') of LED strip lighting under the test-gear shelf over the bench running from a small transformer-based power supply I threw together because the switch-mode power supply units they came with were infinitely noisier than the fluorescent lights - I could barely hear stations through the noise!  Eventually I'll add more LED lighting and run it from solar and a battery...  another project for a rainy day  

Another flash-back - this is how I am remounting the sockets... it looks nice, but the valves don't sit flat due to the size of the bolt heads so I would like to rivet them - but I can't find any suitable brass rivets... I may machine the bots down at some point - I'll see how I go.

This is a newer socket from a parts chassis because the original one was broken.

[Image: http://i241.photobucket.com/albums/ff222...mnkkrl.jpg]

And the first valve in place - the good old 80... and you can see why the masking off of the chassis took so long in the bottom left corner of this pic - masking out the brass was fiddly and took a while, but I didn't want to paint it because its so nice and shiny.
[Image: http://i241.photobucket.com/albums/ff222...jrwop6.jpg]

[kiwi_steve]

Someone asked for coil details... so this is what I have from my notes and measurements - it may or may not be correct but I'll know soon enough I guess

[Image: http://i241.photobucket.com/albums/ff222...yieyeo.jpg]

[Image: http://i241.photobucket.com/albums/ff222...q9kfk8.jpg]

[Image: http://i241.photobucket.com/albums/ff222...l29znx.jpg]

[Image: http://i241.photobucket.com/albums/ff222...xi9o5b.jpg]

[kiwi_steve]

Good news, bad news

 Good news first: The chassis is finally finished, and I applied power for the first time today... Its been on hold while I finished up at my old job - something that sucked my soul dry with 14-hour days, 7 days a week for the last month or so... but finally got back into it today and finished off all the little jobs I've been meaning to do on it to get it done.  Photos to follow in an hour or so - I've got to get them off the phone and I'm typing this up while having a coffee and trying to figure out if I'm wrong about the bad news...

 Bad news: First thing I noticed was excessive HT voltage (well over 400V), no output (well, quiescent amplifier noise when up close to the speaker... then after a bit a lovely bubbling / gurgling sound from the power transformer... removed the rectifier tube and tried again, same... sigh.  Its getting quite hot too.  I know, I know... I should have tested it properly before starting but either way I *will* get this going, but it just got more expensive (especially given how scarce these are here and the 240V mains we have meaning I can't just get one from a slightly more abundant location like the US).

Also, the speaker wiring was messed up - at first I thought it had been replaced but I don't think so - but the wiring had been seriously monkeyed with - maybe to hook up an external speaker... so I spent some time figuring that out and sorting it.  Its got a little bit of something in the voice coil by the feel of it - but the output tx is fine (although the primary is only about 4.2k not the 7.5k from the schematic) and the field winding is good, and on spec exactly.  9V battery test made (quietish) clicks - so I'll call that a win for now.  Its rusty as all heck, so its going to need some love but at least it goes.

Anyway, I'll finish the coffee and think some more...

Steve

[kiwi_steve]

Murphy: 1, Steve: 0

DOH!

(But at least coffee still works)

I discovered on another power-up that there was smoke coming from the chassis underside, and a bit more investigation lead me to find one of the filament wires (first one after the transformer connected to the sockets) going black (it was originally red).  This was with all tubes removed - which made me go "hmmm"... so I started poking about.  And I stumbled across this:
[Image: http://i241.photobucket.com/albums/ff222...vqqbgn.jpg]

This is the socket I recycled into the chassis because someone had removed the 75 and replaced it with some octal tube and I wanted to put it back... and I was looking at how the pin clamps are riveted to the socket... and that made me think - where do those rivets go?  I'll tell you where they go... no, wait... I'll show you:
[Image: http://i241.photobucket.com/albums/ff222...geldsj.jpg]

DOH!

This made me think... where is the insulating layer from this?  Which made me think some more.  At this point I realised what the little tube-socket shaped piece of paxilon (or whatever it is) that I've been stepping over for the last couple of months and meaning to pick up was

[Image: http://i241.photobucket.com/albums/ff222...x1vikk.jpg]

Well, I feel a little stupid... here's hoping I haven't cooked the transformer too badly...

[kiwi_steve]

replaced the cooked wire, modified and inserted insulator and tested... ran up fine with most voltages within about 5% of the listed values. I'm actually pretty amazed that this was the only problem (so far). Its picking up several local stations without any aerial, and a very short (12") piece of wire on the aerial terminal about doubled the volume... most of the trimmers were already near enough to peaked so alignment should be straight forward (well, here's hoping) - I did measure all the capacitance's of the trimmers before pulling it apart, and reset them on reassembly.

I suppose I should do a power up video... thats for another day as I'm heading out... but all good, I'm smiling now

[kiwi_steve]

Steve,

Before you proceed, do check tubes, check transformer with rectifier tube removed, check tubes,  especially rectifiers, electrolytics polarity, and short after rectifier and across all filaments.

<snip>And checking for a short on the filaments is a good idea... I'll do that too since I'm reusing the original wire and it runs all along the chassis edge.</snip>

I was just reading back over this thread... And I just realised that I committed the sins of advice ignored, and promises broken

[kiwi_steve]

So the speaker had a sandpit in it... any thoughts on what I should do here? What happens if I unscrew this to try and clean it up? (I'd just do it and see, but I really don't want to trash a speaker that works when its 82-odd years old...)

Is it ok to give it a bit of a vacuum in around the spider? It feels a little crunchy when moved by hand, but it does sound ok when the radio is playing through it.

[Image: http://i241.photobucket.com/albums/ff222...ypauxd.jpg]

[Image: http://i241.photobucket.com/albums/ff222...uym3m6.png]

[Arran]

So the speaker had a sandpit in it... any thoughts on what I should do here?  What happens if I unscrew this to try and clean it up?  (I'd just do it and see, but I really don't want to trash a speaker that works when its 82-odd years old...)

Is it ok to give it a bit of a vacuum in around the spider?  It feels a little crunchy when moved by hand, but it does sound ok when the radio is playing through it.

[Image: http://i241.photobucket.com/albums/ff222...ypauxd.jpg]

[Image: http://i241.photobucket.com/albums/ff222...uym3m6.png]

Steve;
  It could be sand or it could be rust, if you are careful with a vaccuum cleaner you can try that, though it's nice to have one where you can adjust the speed of the motor so you can crank down the suction. Another way is to just lay the speaker face down and play it till whatever is in there falls out, which may or may not work. As a last resort you could always remove the cone, a little laquer thinner or acetone on the surround/hinge to melt the glue helps, alone with disconnecting the voice coil and removing that center screw from the pole piece. Part of the problem maybe be dirt, sand, or rust, or even just the voice coil alignment.
Regards
Arran

[kiwi_steve]

Thanks Arran, I don't want to disassemble it because its working and it actually sounds fine. Its never going to win any hi-fi awards, but its 80-something years old... I'm quite happy with it just working. I've been playing it face down on a piece of cardboard on and off for the last few days so it will be interesting to see whats on the card when I remove it. I don't think I will vacuum it just in case I dislodge something and it jams against the voice coil.

Can that centre machine screw be safely removed for de-rusting or will that potentially mess up the alignment of the coil?

Cheers

[kiwi_steve]

I just realised I never posted any topside finished photos... here are a few.  Apologies for the quality, taken at dusk and the phone was going flat and wouldn't let me use the flash...

From this:

[Image: http://i241.photobucket.com/albums/ff222...bt6zo0.jpg]


To this:

[Image: http://i241.photobucket.com/albums/ff222...qgfkg1.jpg]

[Image: http://i241.photobucket.com/albums/ff222...r7iqiw.jpg]


And from this:

[Image: http://i241.photobucket.com/albums/ff222...rcem03.jpg]


To this:

[Image: http://i241.photobucket.com/albums/ff222...haxehe.jpg]

[kiwi_steve]

I'm pretty sure I was supposed to post a power-up video quite some time back... here it finally is

https://youtu.be/FJ6AfDRtgbw