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 The little general that maybe never was
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 Return to top of page · Post #: 16 · Written at 9:01:03 PM on 28 July 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

Thanks GTC.
That is absolutely awesome.
Can't wait to get stuck in .It even has a point to point wiring layout what more could you want.
Thanks to all of you well done Lance in finding it .
Regards Jim


 
 Return to top of page · Post #: 17 · Written at 9:15:58 PM on 28 July 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5254

This is an English version: https://frank.pocnet.net/sheets/046/e/EBF2.pdf

As I notes elsewhere this week, grid resistors on audio output valves especially 6V6 is common & checking plate resistors on the first audio is also mandatory. I would expect that to be reflexed, as the 6V6 needs around 1.5V of drive, & EBF2G is going to be supplying it.

5Y3G series & # 80 are the same tube with a different base: I would consider a heat shield if you change albeit I have a dud #80 in a GT on the bench.


 
 Return to top of page · Post #: 18 · Written at 1:44:27 PM on 31 July 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

Thanks for that Marcc.
Well today I am making a start. I think I will remove the above chassis items mask the valve bases and give it a paint job.
The power tranny meggers ok I am thinking of giving the tranny a spray with Esterpol varnish I think that should be ok then a spray paint job with rustgauard paint grey finish.
Regards Jim.


 
 Return to top of page · Post #: 19 · Written at 2:37:34 PM on 31 July 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

I hope I bought a suitable pressure pak varnish for the transformer, please tell if not. Cabot's Cabothane clear polyurethane.Oil Based.
Regards Jim


 
 Return to top of page · Post #: 20 · Written at 4:06:59 PM on 31 July 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2370

Oil based poly is good.

Do you want that smaller GT-style 80?


 
 Return to top of page · Post #: 21 · Written at 5:52:22 PM on 31 July 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

Hi Ian.
No,but thank you for the offer I have several N,O.S.
I fully understand what you are saying about the big fella cooking the power transformer and when if ever it gets back together I will fit the GT type. It is a shame because some of the appeal to me is those big old bottles I love their shape.
I tend to like the back view more than the front !
Well what a mess, I had no choice but to strip everything off the chassis .The chassis is now completely bare. There are only two salvalagble valve bases the 4 pin base for the 80 and one Bakelite octal socket the lugs off the pins have been previously busted off with the leads just soldered to the stubs . I may have some,I guess N.O.S. are not likely to exist . The I.F. transformers are also a bit sick the plastic bits on the underside of broken away I can probably fix them. I will have to add a choke ,I have some, the original setup was with a field coil type speaker. Like all the other missing bits there is no speaker. Not to worry, I have some 5inch speakers and some chokes .
It can't be completely as per original 1946 circuit but I want it as close as possible. It is nice having that article it has given me the inspiration I would have had as a teenager. In actual fact I was minus one back in 1946.
I will derust the chassis and give it a coat of grey paint. Not sure if I should do the underside it is pretty clean and I will need to scape it here and there for earth connections etc. I will be fitting some tag strips to keep it tidy.
Regards Jim


 
 Return to top of page · Post #: 22 · Written at 6:27:45 PM on 31 July 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1250

Hi Jimb use my "1946 little general" in the special projects section Jan 2017 for inspiration!
I tried out all sorts of things in that one that may be relavent to your re-build!

Cheers, Fred.


 
 Return to top of page · Post #: 23 · Written at 6:38:23 PM on 31 July 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

Thanks Fred I will check it out.


 
 Return to top of page · Post #: 24 · Written at 8:46:02 PM on 31 July 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

Hi Fred that is an amazing effort you did a great job.
Mine will be a lot less awesome than that I am just trying to piece it back together as per the original article . I don't have your level of skill and expertise . The chassis is now completely stripped. I will be making some of the holes larger where the transformer wires go through the chassis so I can fit grommets and some more holes so I can add some tag strips . Then some derusting and paint.
This will take me quite some time and the results won't be nearly as stunning as yours but it is keeping me occupied and out of trouble I hope. It is always good to have some sort of a project to think about, it takes your mind off other stuff .
Regards Jim.


 
 Return to top of page · Post #: 25 · Written at 5:08:09 PM on 3 August 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

Well I ended up completely stripping the chassis one of the valve bases had its solder lugs torn off and the wires were soldered to little stub pieces . I have made an adaptor plate so I can fit a newer octal base in its place. Wire brushed the chassis and it has a nice new coat of grey paint . Run into some choke troubles . I pulled one of a gutted chassis I was given however it measures 300k ohm so it is obviously no good. I then found another with no chassis mounting I have made up amounting but not sure what it came from or its suitability. I would appreciate your thoughts it has stamped on the top 15 watts . 50 C . Using an analogue meter it measures 22 ohms ,on a digital meter it measured 25.6 ohms and 448 mH would this be suitable?
I would think wattage wise 8 to 12 watts for the high tension , would that be right ? I think the HT current should be around 40ma for a four valve radio I could be showing my lack of knowledge here these are my thoughts only.
Anyway this afternoon I visited Tony H and took back a couple of radios I repaired for him and I managed to pick up an old chassis not sure what it came from but it has an 5 inch fieldcoil speaker in it, what a bonus this could be! The cone has a nasty tare in it and I haven't removed it as yet from the chassis so I don't know if it is electrically ok yet.
Regards Jim


 
 Return to top of page · Post #: 26 · Written at 6:46:09 PM on 3 August 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1250

Hi Jim, typically HT chokes have hundreds of ohms and Henrys of inductance, not low ohms and mH.
I have wound small chokes using wire that can handle 50 ma or so.
Thats pretty fine wire!
You have the current draw about right.

That speaker sounds like just the job, the excitation coil will probably have hundreds of ohms and 10's of henrys in it.
Hope all the coils are intact.
Put a band aid on the cone tear and you are in buisness.

Keep going matey, a coiuple of sets like that and you will be an expert!!!!!

Fred.


 
 Return to top of page · Post #: 27 · Written at 7:14:06 PM on 3 August 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

Hello Fred thank you, I have never had to analyse the properties of a choke . So ok this is not going to do the job that is pretty clear from your comments. When I have time I will pull this speaker out. I may have to get more advice on the speaker repair if if is electrically ok.
On one of your posts you used some sort of latex. My speaker repairs are less than brilliant.
Regards Jim.


 
 Return to top of page · Post #: 28 · Written at 9:25:01 AM on 4 August 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1250

Jimb, there are all sorts of favourite methods to repair tears in cones.
Sometimes you also have to replace missing material as well.

The aim of the repair is to put the shape back in cone and stop the air from whistling through the gap.
Thus I have seem stuff like sticky tape of various kinds, medical micropore or similar, anything highly adhesive and flexible.
Where the cone material is rotting away painting the cone to bolster the fibres "put some life back into it" can preserve the ridigity and the shape with a latex base or even a glue type substance from Woolies or Bunnings will work.

This is where I stop and answer the guy down the back of the room who is hopping up and down spouting about the fidelity constants of the cone and all those theoretical equations to do with golden ears enclosures and frequency response, Q, Thiel constants and all that.
Give me break fella's, these are 5" crap speakers bolted onto a steel chassis vibrating about un baffled!

I have a big bottle of water base latex "gorilla snot" that dries clear and forms a flexible skin and penetrates about 34.7856 microns into the fibres and SAVES a cone from disintergrating completely when brushed on in one or two layers. If a big chunk of cone or surround is missing, I fold in bits of tissue paper and brush in latex to fix it in position. A mist coat of black rattlecan paint can make it all look perfect. Just like doing fibreglass repairs on a car.

No I do not suggest that your Axiom or Goodman quality driver in an enclosure can be fixed that way, totally different area of audio reproduction! Those speakers go off to an expert who restores speakers by re-coning and re-building.

All good fun.
Fred.


 
 Return to top of page · Post #: 29 · Written at 12:00:05 PM on 4 August 2020.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 544

Well said Fred,
We have far too many audiofools and armchair super techs.
I like the practical approach where it is needed.
Not many of us left I’m afraid.
JJ


 
 Return to top of page · Post #: 30 · Written at 2:38:43 PM on 4 August 2020.
Jimb's Gravatar
 Location: Kanahooka, NSW
 Member since 18 November 2016
 Member #: 2012
 Postcount: 712

Ok I removed the speaker from the doner chassis . It will be a very tight fit because the chassis is very small. Under normal circumstances I think it would be salvalagble the field coil measures 1963 ohms and 16.3 H. The speaker primary is 493 ohms and 6.65 H.
I am not convinced I can fix the cone . None of the cone is missing which is a good thing,however it has a radial tare from the outer circumference to the centre just beyond where the wires to the excitation coil are glued into the cone. It has another tare that extends around the circumference for about 1-3 of the cone's circumference . I usually end up worse off trying to fix these because of the lack of control I have with the shakes at times you would think I was using a jackhammer , not a tube of glue.
Fred I still have no idea what this latex stuff you use. Does it have a name and who sells it ? Is it contact adhesive of some kind?
Maybe I need to go to Toranga Park zoo and find a gorilla with a head cold .
These speakers are so rare if I stuff it up that's it. I remember many years ago using a product called Bostic Indont think it is around anymore it probably morphed in silastic.
Regards Jim


 
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