Info Needed for Little Maestro 10 AC/DC

[John G8MWF]

Originally Posted by Sideband

If I can I'll have a look at mine tonight. I'm pretty sure there is a 100 ohm resistor in the anode of the rectifier. At least mine hadn't been got at at all. I'm the only one who has kept it going.

That would be really helpful - thank you.

I am sure that the repair or alteration made in the past was made with the best intentions but I would feel much happier knowing the way it was meant to be.

[John G8MWF]

Originally Posted by ms660

Hope this helps.

Hello Lawrence,

I may need to use this information later if things go wrong but right now I am happy trying to put it back to the way the manufacturer made it - which version it turns out to be!

Thanks again.

John

[ms660]

No problem, what's going to happen with the valve base skirts?

Lawrence.

[John G8MWF]

Hello Lawrence,

I am trying not to touch them until I get the HT sorted out and then see if they work. It really is a shame that getting replacements is so expensive now!

Is it possible to glue/cement then in place? That would be my choice if it is.

The one thing I am learning is that Trader Service Sheets are a bit like the Oracle - unreliable!

I have the AC version of this set waiting in the wings, sheet 912, and there are so many differences from the sheet in the L1 - L4 and S1 - S6 area that I have had to draw it out to make sense - and it doesn't!!!

Cheers

John

[ms660]

Some Trader sheets do have errors, but sometimes they have more useful information in them than the manufactures manual such as various modification revisions etc.

Manufactures manuals tended to be shoved out around product release time then amendment/error sheets shoved out later after all the snagging, the results of the snagging period in many cases was based on the service techs moans/groans/findings when they were out in the field or on the bench, many of those mod sheets etc have not survived.

Many original manufactures manuals contain errors, I speak from my experience in the servicing trade.

Lawrence.

[John G8MWF]

I was just looking over other sheets for the Little Maestro and found that the diagram for the De Lux, service sheet 871, is a closer match to my set than the information in sheet 913!

So, was this due to manufacturing or the actions of a repair engineer who decided what was better a long time ago?

Any ideas?

Cheers

John

[usradcoll1]

Originally Posted by John G8MWF

I am trying not to touch them until I get the HT sorted out and then see if they work. It really is a shame that getting replacements is so expensive now!

Is it possible to glue/cement then in place? That would be my choice if it is.

I first found the valve base skirts cracked and appeared the same way. Brand new one in the carton. They're made of brass!
All I did is lined up the crimps with the bakelite base and wrapped wire tightly around the base and soldered it together, where the crack is.

[ms660]

Originally Posted by John G8MWF

I was just looking over other sheets for the Little Maestro and found that the diagram for the De Lux, service sheet 871, is a closer match to my set than the information in sheet 913!

So, was this due to manufacturing or the actions of a repair engineer who decided what was better a long time ago?

Any ideas?

There is clearly an error in the 10 AC/DC trader sheet schematic as I already pointed out earlier, that to me seems to be what's caused confusion for the OP.

The Deluxe model I would say is the forerunner of the 10 series models but note that it's heater dropper resistor is a Line Chord type, not a chassis mounted resistor....

Which ever way you cut it you have to remember that many manufactures did all sorts of changes to many models...without notification, which sometimes left the service techs scratching their heads when comparing what was in front of them to what the manual was telling them....Sometimes troubleshooting isn't painting by numbers

Lawrence.

[ms660]

Originally Posted by usradcoll1

I first found the valve base skirts cracked and appeared the same way. Brand new one in the carton. They're made of brass!
All I did is lined up the crimps with the bakelite base and wrapped wire tightly around the base and soldered it together, where the crack is.

Looks like the same disease as with the famous Hallicrafters SX28A S meters.....

Lawrence.

[John G8MWF]

Originally Posted by usradcoll1

I first found the valve base skirts cracked and appeared the same way. Brand new one in the carton. They're made of brass!
All I did is lined up the crimps with the bakelite base and wrapped wire tightly around the base and soldered it together, where the crack is.

Sounds like a good plan to me - thank you.

I also wondered if there was a modern glue/cement that could be used in conjunction with your suggestion to improve the seating of the valve?

[Boater Sam]

I've had sets with completely different chassis fitted from new. I suppose that old chassis were used up on later model upgrades and newer chassis fitted to older models to clear cabinet stocks.
There were lots of variations of the Little Maestro anyway.

[John G8MWF]

That makes sense. I keep forgetting how old these sets are and how manufacturing operated back then.

I am, still, convinced that this chassis is 'almost' the same as sheet 913 as all of the values follow this sheet and the replacement R16 has been setup for around 830 ohms.

R14 is so badly discoloured that it is hard to tell what it was originally. So wiring it back up with the correct resistor is my priority - something to keep me quiet for a while!

Thanks for your help



John

[usradcoll1]

Originally Posted by John G8MWF

Sounds like a good plan to me - thank you.

I also wondered if there was a modern glue/cement that could be used in conjunction with your suggestion to improve the seating of the valve?

I generally will use a small bead of silicone sealant before reseating the skirt, wrap it tightly with the wire, but wait to solder it, until the sealant sets up.

[usradcoll1]

Originally Posted by ms660

There is clearly an error in the 10 AC/DC trader sheet schematic as I already pointed out earlier, that to me seems to be what's caused confusion for the OP.

The Deluxe model I would say is the forerunner of the 10 series models but note that it's heater dropper resistor is a Line Chord type, not a chassis mounted resistor....

Which ever way you cut it you have to remember that many manufactures did all sorts of changes to many models...without notification, which sometimes left the service techs scratching their heads when comparing what was in front of them to what the manual was telling them....Sometimes troubleshooting isn't painting by numbers

Resistance line cord droppers were used a lot from 1933-39, or until the 150ma valves were developed. The small 4 or 5 valve, AC-DC receivers of the day were usually TRF and were referred as "Depression Radios", as they were rather depressing. My opinion only, but still fun to collect.
The lowest priced ones used pin-drive magnetic speakers, that didn't need an output transformer. Those sets had that "tinny" sound.

[John G8MWF]

No hint of asbestos in the line cord - so I don't think that is a dropper. But the diagram of the deluxe shows the limiting resistor connect at the source of AC - but presumably the whole cord is resistive so how can that be?

Arghh!

[Herald1360]

Some line cords had an extra wire in the bundle to carry full mains to the set as well as neutral and the inline flexible dropper for the heater chain. Useful on early US sets where the heaters didn't even add up to 110V and for UK sets where the higher HT was useful for the output stage at least.

[Boater Sam]

Used to have great fun when people had tried to put a 13A plug on one of these 3 core line cords! Funny, they never got them to work!

[usradcoll1]

Originally Posted by Boater Sam

Used to have great fun when people had tried to put a 13A plug on one of these 3 core line cords! Funny, they never got them to work!

Radio owners here would abuse the resistance cords by yanking the cord to remove the plug from the receptacle, instead of pulling it by the plug. I seen, very few of them with the original plug.
People tried to replace the plug themselves and would miss the tiny resistance wire.

[Sideband]

Originally Posted by Sideband

If I can I'll have a look at mine tonight. I'm pretty sure there is a 100 ohm resistor in the anode of the rectifier.

A little late but I've now taken some pictures of under the chassis. The layout on mine is slightly different to yours as the dropper is on the RH side.

First shows general layout underneath. Second shows the 100 ohm limiter resistor connected to the anode of the 35Z4GT. Third shows the 1.5K smoothing resistor and the 10K common screen feed resistor. Forth shows the 100 ohm pilot lamp shunt. Fifth shows the top chassis layout....the dropper is in a different place.

[John G8MWF]

That's what I needed - a big thank you.

So . . . . the anode goes to the mains via a 100 ohm resistor. And the mains joint on the 100 ohm resistor is then connected onto the dropper resistor.

And just for a sanity check are you using, I suppose you must be, a 35Z4GT rectifier?

My 'layout' conforms to that in service sheet 913.

I do NOT have a heat shield on my dropper which explains why the back cover is burnt and crumbly and broken.

Your chassis is a LOT cleaner than mine!

So after all of these discussions it looks like, in my opinion, that Service Sheet 913 is wrong or not the correct revision for this set. AND there are a LOT of different versions of this model.

My new 35Z4GT should arrive on Monday and I am replacing wax caps and cleaning up the mess and then I can find out what else needs doing.

Once again thank you.


John