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 Post subject: Radiola Grand Restoration - Working!!
PostPosted: Jan Sat 25, 2020 3:53 am 
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I'm working on a Radiola Grand and I have one transformer with a bad secondary, which isn't bad out of three transformers. I'm sending it to Heyboer to rewind and I can not tell by the old schematics what the spec should be (1:3, 1:5 etc.) Also the 22M ohm reading on the input tertiary winding seems high, I've never run across a battery radio with that high a DC resistance. Your thoughts?

Schematic...

Attachment:
Radiola Grand Schematic.jpg
Radiola Grand Schematic.jpg [ 555.94 KiB | Viewed 1992 times ]



Readings....

Output (L)
Primary – 625 ohms
Secondary – 802 ohms
Tertiary – 982 ohms

Input (K)
Primary – 5.65K ohms
Secondary – 1.148K ohms
Tertiary – 22M ohms

(H)
Primary – 942 Ohms
Secondary - Open

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Last edited by atwaterkent1 on Apr Tue 28, 2020 12:52 am, edited 8 times in total.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Sat 25, 2020 4:18 am 
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IMHO I would think 3:1, center tapped. The 22meg is leakage across open ends of a winding...

Let Heyboar do the discovery of the winding resistance/ratio.

Schematic is not much different than a Radiola IIIa,

Chas

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Sat 25, 2020 6:05 am 
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Thanks Chas, I will do that if I have to. I'm hoping someone with the same radio in working condition will provide the missing information. None of the transformers is center tapped, two have three winding's and six leads and one has two winding's and four leads.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Sun 26, 2020 9:11 pm 
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Dan, you are saying that your Radiola Grand transformers do not match the schematic? The Grand on RM shows the transformers to have 5 terminals, both center tapped one side.
22 Mohm tells me that transformer is bad.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Mon 27, 2020 1:32 am 
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Jeff - The Schematic is correct, two of the transformer leads go to the same center terminal.

Attachment:
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I've sent an email to Heyboer Transformer asking if they can figure out the third winding by inspecting the transformer, if they can't I have a problem.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Mon 27, 2020 5:35 pm 
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OK, got it. That is effectively a winding (1 to 5) with a center tap (3), made up of 2 windings, 1 to 3, and 3 to 5, connected together in series at 3.
Attachment:
Untitled.jpeg
Untitled.jpeg [ 27.09 KiB | Viewed 1824 times ]

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Mon 27, 2020 11:37 pm 
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Now I just need to know what the value is for the tertiary (third) winding.

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Last edited by atwaterkent1 on Jan Tue 28, 2020 8:00 am, edited 1 time in total.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Mon 27, 2020 11:59 pm 
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I am not clear on which transformer this is. Is it “K” or “L”?
In your measurements you have input and output reversed; input is K and output is L. Can you put numbers on your measurements (I.e., 2 to 4, 980 ohms)? Not sure what the tertiary winding is.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Tue 28, 2020 1:50 am 
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atwaterkent1 wrote:
Thanks Chas, I will do that if I have to. I'm hoping someone with the same radio in working condition will provide the missing information. None of the transformers is center tapped, two have three winding's and six leads and one has two winding's and four leads.
No problem, it is single ended driver to push/pull input then, push/pull output to high impedance output (like 2K).

The AES "universal" Radiola-IIIa transformer windings would work, but that is not a suggestion I would use. I prefer my AF transformers to have not only impedance but resistance like the OEM...

Worst (IMHO) that could happen at Heyboar is to swap a phase of the dual primary or secondary depending which transformer one is looking at if they wound as a single winding and not a tapped one.

That could be corrected at home, swapping a pair of coil wires.

I think Dave Slusarczyk has a Radiola Grand... Send a PM....

Chas

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Wed 29, 2020 12:16 am 
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Here's a very poorly made drawing of the connections :oops:

Attachment:
Radiola Grande Transformer Connections.jpg
Radiola Grande Transformer Connections.jpg [ 615.56 KiB | Viewed 1750 times ]



Output
A to D = 625 ohms
B to E = 802 ohms
C to F = 982 ohms

Input
A to D = 5.65K ohms
B to E = 1.148K ohms
C to F = 8.4K ohms (I cleaned up one of the lead ends that seemed to have a sticky substance in it and now I get what I believe is a good reading.)

Each lead has continuity to only one other lead, wouldn't a center tap have continuity with two other leads?

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Fri 31, 2020 2:34 am 
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I put the two good transformers back together, they definitely have three separate windings. Here are the readings....

Attachment:
Radiola Grande Transformer Readings.jpg
Radiola Grande Transformer Readings.jpg [ 700.54 KiB | Viewed 1694 times ]

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Last edited by atwaterkent1 on Jan Fri 31, 2020 3:39 am, edited 1 time in total.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Fri 31, 2020 3:13 am 
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Dan,

Agreed, the transformers have three windings. Two windings on each transformer physically share a common external connection, therefore become a center tapped winding over all.

The output transformer seems to behave very strangely with a 800k + reading.

Are you measuring these with a DVM?

Try an analog ohmmeter...

Apparently there does not seem to be isolation between the primary and the secondary froms your readings...

I say outright there is no "magical magnetics" going on.

They are push/pull input and push/pull output.

There could be something unique to the failure, like a pulse induced burnout followed by 80 years of "rotting" in the acids created from a burnout...

Certainly, Heyboar can sort it out. Send the a copy of the schematic too...

You could experiment: Get, beg, borrow any small PP input/output transformers better if 20's era like Coto, Amertran, Thordarson even a pair of ARBE Radiola IIIA's and tack them in see how it plays, use sub 99's, 864's, 30's. That will give confidence there is nothing strange going on...

Chas

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Fri 31, 2020 3:40 am 
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Oops... make that .802K ohms, sorry about that Chas. :oops: All readings checked with a Fluke.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Fri 31, 2020 4:19 am 
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atwaterkent1 wrote:
Oops... make that .802K ohms, sorry about that Chas. :oops: All readings checked with a Fluke.
Oh, then its not ohms its flukes :|

If that is the case, the transformers are not open on any winding...

I know you have reassembled them, so, un-solder the co-joined windings at the "center tap". Then take resistance reading of each of the three windings.

This time find an analog meter, Simpson Triplett etc any ohms/volt 5k to 20k is O.K.

Now what I expect is that every winding will have roughly 5 to 10K ohms resistance. I do not expect the windings that use the center tap to be alike, as it is the turns, not resistance that is important. The output transformer, output winding may be lower resistance, maybe not. Having identical transformers is generally the rule but there are exceptions.

It would be interesting to do a leakage test (at low voltage) this will appear as a very high resistance.

Take each pair of windings and clip-lead the ends together. Doing so removes the possible adding of the winding resistance to the leakage. Set the analog ohmmeter to the highest scale and check across the jumped coils, the very innermost coil to the frame, the inner to the mid and the mid to the outside coil.

If they are all well beyond the meter range, say infinity. the coils are not leaking to each other an the laminations.

If all "seems" well, tack them back in the radio, plug adapters in the sockets and stick some of those $10 type 30's in. Use the ARBE and set the filament for 2 volts, the battery rheostat will not control very effectively because of the 60ma filament current. None the less, apply all the OEM plate and grid volts and see if the radio works...

If not, bad transformers will be missing plate voltages or strange grid voltages. That dynamic test will be final confirmation...

Rewinding is costly, sending good transformer to be rewound, Oops...

GL

Chas

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Jan Fri 31, 2020 5:26 am 
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Chas - The third transformer, which definitely had a bad winding was shipped out to Heyboer today. I'll try running some of the other tests you mentioned.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Feb Sat 01, 2020 6:05 am 
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I like the early Radiola/Aeriola transformers


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 Post subject: Re: Radiola Grande Restoration
PostPosted: Feb Mon 03, 2020 1:22 am 
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Certainly more work to replacing the rubber tube mount supports than on the other Radiola's. Two on each side of the plate the tube sockets are mounted on and one of the tube sockets has its own rubber supports. Disconnected and tagged eight more leads to get at the parts holding done the rubber supports on the tube socket. It would be worse if the transformers weren't out already since they also attach to the tube socket mounting plate, the added weight would have been a problem.



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 Post subject: Re: Radiola Grande Restoration
PostPosted: Feb Fri 07, 2020 9:35 pm 
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Chas wrote - "I know you have reassembled them, so, un-solder the co-joined windings at the "center tap". Then take resistance reading of each of the three windings.

This time find an analog meter, Simpson Triplett etc any ohms/volt 5k to 20k is O.K.

Now what I expect is that every winding will have roughly 5 to 10K ohms resistance. I do not expect the windings that use the center tap to be alike, as it is the turns, not resistance that is important. The output transformer, output winding may be lower resistance, maybe not. Having identical transformers is generally the rule but there are exceptions."

Results - (With Simpson, ohms check around 50 ohms less than my previous posting on readings for the Output and Input transformers.)

Chas wrote - "It would be interesting to do a leakage test (at low voltage) this will appear as a very high resistance.

Take each pair of windings and clip-lead the ends together. Doing so removes the possible adding of the winding resistance to the leakage. Set the analog ohmmeter to the highest scale and check across the jumped coils, the very innermost coil to the frame, the inner to the mid and the mid to the outside coil.

If they are all well beyond the meter range, say infinity. the coils are not leaking to each other an the laminations."

Results - (No leakage found on any windings)

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Feb Sat 08, 2020 2:12 am 
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New rubber supports installed. The original screws that held the two metal brackets on each side were too short to work with. Even though the new rubber strips were actually a bit smaller than the originals, it was impossible to squeeze them down enough to get the screw started into the bracket so I had to buy replacements that were slightly longer. When they put the originals in they must of been made out of a softer rubber or had some way to squeeze them down far enough to get the screws into the brackets. I also had to cut notches for the screws to get the strips close enough together for the brackets to go over them both. With the brackets clamped over the notched area I'm not worried about the bands breaking when installing or removing tubes.
Tomorrow, hopefully, I'll reinstall two of the transformers then set the radio aside until I get the third one back from Heyboer.

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Chas, Jeff, thanks for the help. I'll update the thread when the transformer gets back from rewinding.

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 Post subject: Re: Radiola Grande Restoration
PostPosted: Mar Sun 22, 2020 1:44 am 
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Transformer back and installed. I'm ready to hook up the ARBE, but this radio has a very unusual wiring set up. First,there are four connection terminals for the filament power so I suspect wiring them in a parallel circuit is the way to go. Next is the B voltages with the schematic showing 45v and 90v. B- seems to be the same terminal as the ground on the back (the label is worn and unreadable except for the word ground). B+, 90v is a terminal next to a large condenser in a black metal box (there's an original wiring tag on one of the wires coming from that terminal). Next is the B+, 45v. No clear markings or tags for that one. Schematic shows it going to the #2 terminal on the audio output transformer. The only wire coming off that terminal goes into a wiring bundle. Checking the ends of the wires coming out the other end of the bundle shows continuity with only one wire going to the A3 terminal on the back. That would meant the B+, 45v going to the same terminal as the A+ filament power. Can't be right, right?

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Inside - Condenser and Terminal

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