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Old 11th June 2017, 05:53 PM   #1
Turbon is offline Turbon  Sweden
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Default Parmeko opt transformers

Hi.

I have tried to Google for information about these opt's but haven't found anything. The pic shows me that they are 9k trafos which can give 7W.
The secondaries are quite clear but I don't quite understand the primary side.
Please enligthen me

Regards

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Old 11th June 2017, 06:44 PM   #2
kevinkr is offline kevinkr  United States
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A multimeter would answer the question pretty quickly I think. I think this is a PP transformer.

T1 and T2 are taps - probably screen grid for UL operation.

IP - I think is the in phase plate (relative to the tap used for feedback on the output)

OP - I think is the out of phase plate (relative to the tap used for feedback on the output)

CT - Center tap

If you need assistance for their thoughtful disposal just send them to me....
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Old 11th June 2017, 06:47 PM   #3
kevinkr is offline kevinkr  United States
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These seem very generously sized for a 7W transformer, I'd suspect they would make an excellent match for a pair of EL84s in a very conservative application. (10W or less) Maybe used with something similar to ELL80?

Confirm taps with meter?
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Old 11th June 2017, 07:07 PM   #4
Turbon is offline Turbon  Sweden
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Thanks Kevin.

I will measure them when I get time to focus on the task .

Regards
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Old 12th June 2017, 02:09 AM   #5
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what i do with unknown traffos is to inject a low voltage of say 6 volts on the 15 ohm secondary, then measure the voltage from ct to the other taps....
or from IP to OP, then once voltage ratio is known, then the impedance can be calculated...
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Old 12th June 2017, 07:48 AM   #6
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Thanks Tony.

Yes I've read about the technique at another site. I will try to find it again.

Regards
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Old 12th June 2017, 08:11 AM   #7
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Quote:
Originally Posted by TonyTecson View Post
what i do with unknown traffos is to inject a low voltage of say 6 volts on the 15 ohm secondary, then measure the voltage from ct to the other taps....
or from IP to OP, then once voltage ratio is known, then the impedance can be calculated...
Transformers don't have impedances
They have winding ratios
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Old 12th June 2017, 09:15 AM   #8
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sure, that should be reflected impedance......
from turns ratio, reflected impedance can be taken...
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Old 12th June 2017, 04:10 PM   #9
kevinkr is offline kevinkr  United States
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The ratios can be calculated since the impedances are known, my suggestion was mostly to confirm by resistive measurements whether my basic premise was correct or not.

Carrying it a step further and determining the ratios would be useful to determine the % tappings of those two taps and indeed that they are connected to the primary winding. Also of course it would verify that the transformers are electrically good before proceeding with a fairly expensive project without that assurance.

They should be very nice transformers..
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Old 14th June 2017, 06:23 PM   #10
Turbon is offline Turbon  Sweden
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Hi

Measured the resistances:

Opt 1:

CT - T1 = 114,6R
CT - T2 = 94,8R
CT - IP = 475R
CT - OP = 472R
IP - OP = 948R

Opt 2 showed a break at first between CT - T2 and OP...
Opened it but it looked very fresh and I measured at the solderings - it came alive so there is a bad solder joint somewhere. I'll take care of that later.

CT - T1 = 116R
CT - T2 = 94,8R
CT - IP = 484R
CT - OP = 484R
IP - OP = 971R

The outputs shows 1R 1,1R and 1,2R on both.

So they are probably ok

I will make the AC test in the weekend.
Will an AC wallwart be ok? How much current is needed?

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