Help with replacement output transformer for Kriesler 11-20
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Location: Toongabbie, NSW
Member since 19 November 2015
Member #: 1828
Postcount: 1313
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I second every thing Ian has said.
I have used the Jaycar line tranny as a general purpose unit for OPT use.
Have also used Jaycar power transformers as OPTs.
So long as the turns ratio is close you will get music.
Sure if you want laboratory standard performance, maximum power transfer, optium bandwidth...bss...bs ....bs, THEN you have to use something better.
Like when you are matching PP output valves in a guitar amp for max output in the 100's watts or for the "golden ears" with an "ultra linear" circuit.
In a radio with a couple of watts max, anything will work, so long as it has some iron and some copper in it.
Fred.
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Location: Ballarat, VIC
Member since 4 July 2018
Member #: 2260
Postcount: 15
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Ahhhh 100 volts RMS max output!
Gotcha!
That makes perfect sense now that it's spelled out.
Your a life saver... or a Radio saver!
Thankyou, Rick
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Location: Ballarat, VIC
Member since 4 July 2018
Member #: 2260
Postcount: 15
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Thanks Fred for the info.
I may come to use it again in the future!
I tend to be a bit cautious/curious with the output transformer because I wondered why
mine was 'dead' in it in the first place.
Like David's video above, his was dead too.
The coupling cap was 'fried', but the 6V6 seems to be 'ok', even the old filter caps checked out ok, but admittedly, not tested under high voltage.
It's one thing to replace, but equally nice to know why to avoid in the future....
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Location: Kanahooka, NSW
Member since 18 November 2016
Member #: 2012
Postcount: 712
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In regards to cleaning up the case I find extra cut auto polish does a good job on dulled bakelite. It is only my suggestion there may be valid reasons why you should not use it .
Regards Jimb
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Location: Wangaratta, VIC
Member since 21 February 2009
Member #: 438
Postcount: 5389
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A lot of that auto polish has Silicon in it which becomes a curse at the cutting compound is Sodium Bi Carbonate (aka Baking Soda) which can get into the pores of the Bakelite: Itself dulling it by leaving a white residue. The Silicon repels the vinegar needed to get rid of it.
Also keep Soda Ash away from Bakelite it does like attacking it; That's why I suggest being as fast as you can, when using a mix of it & dishwashing liquid, aided by a small brush, to remove mouse doo from wafer switches.
As noted many times the chances are around two in ten of finding a Kriesler that has not got a dud output transformer; Its an attrition rate.
Marc
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Location: Toongabbie, NSW
Member since 19 November 2015
Member #: 1828
Postcount: 1313
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Just to confirm the use of a PT as an OPT on a mantle radio.
On my Kriesler 11-60 repair,
I used a Jaycar MM2013 240/12v PT and a Jaycar AS3007 5" 4 ohm speaker to replace the Rola 5C speaker and OPT.
The Jaycar speaker bolts straight into the same holes as the Rola.
The MM2013 is larger than the original but I mounted it beside the speaker where there is plenty of room.
The 6M5 valve swings 150v RMS on the PT primary when set to deliver 3vRMS into the speaker.
That about 2 watts of power output which equates to LOUD to the ear.
The MM2013 has 12 henry inductance and 450 ohm resistance. I left the laminations interleaved so you just bolt it straight in
The 6 volt tap suits 4 ohms best.
We are not talking about Hi-Fi here, the distortion levels introduced from the diode detector onwards give a THD content around 10%.
That is normal for a valve radio with a diode detector and single end output.
At about $10 for each item why would you do any thing else?
Obviously for higher powered amps with PP outputs and radios with low distortion detectors you use a class up on speakers and transformers. Then I wind an OPT to suit and bolt in suitable speakers.
Fred.
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