MOT's as output transformers?

ak_47_boy · 14th September 2007, 02:53 AM

How would a few microwave oven transformers due for output transformers? They have a independence of 2200 ohms with a 8 ohm load. They could do as HV chokes also?

rcavictim · 14th September 2007, 03:08 AM

They work well as chokes. Not so as ouput iron. I thought one might do just what was wanted in a guitar amp...distort. Not even good enough for that application, the HF response is non existant.

martinab2 · 14th September 2007, 06:27 AM

Useless as an output transformer unless you want bass only. Made quite a reasonable (if heavy and bulky) plate choke in a 2a3 parafeed amp. Current limiting shunts are best removed first.

rcavictim · 14th September 2007, 07:39 AM

I have used them with success without removing the magnetic shunts (but I agree that you should) in a breadboarded 6080 (several in parallel) parafeed amp.

sorenj07 · 14th September 2007, 02:11 PM

Why not just choke-input filter the MOT to get around 1700-1800VDC. Rectify with a couple TV damper diodes? You could probably run some big tubes in SE with that kind of power. Don't MOT's also have filament heaters?

p.s. please don't die.

croccodillo · 14th September 2007, 03:03 PM

Quote:

Why not just choke-input filter the MOT to get around 1700-1800VDC. Rectify with a couple TV damper diodes? You could probably run some big tubes in SE with that kind of power. Don't MOT's also have filament heaters?

You'll get about 2100V once rectified, at about 650mA.
But this is not a good idea, for a few reasons:

1. MOT are not rated to work continuously, they will not last too long.

2. Filament heater voltage for magnetrons is of about 3.3V@12A, not so useful for audio thermoionic valve (unless you double, rectify and regulate it).

3. MOT are prone to hum and to mechanical vibrations after a short time of life (they are not made for audio, but for kitchen ovens...).

4. I never seen a MOT in which you can remove the magnetic shunt; without removing it, however, the transformer is not so good.

5. One of the secondary end is directly connected to the MOT core, and thus the insulation of such an end is not so good with respect to ground, making it quite difficult to rectify the output voltage with a full bridge (you must keep the end connected to ground, and thus you can only rectify the voltage using an half wave with a single HV diode).

Ciao,
Giovanni

sorenj07 · 14th September 2007, 10:12 PM

you could also cut the core apart and re-wind a new bobbin for it, to make it a choke or more manageable voltage.

ak_47_boy · 14th September 2007, 10:36 PM

I would but they are always welded.

Geek · 14th September 2007, 10:58 PM

Angle grinder can take care of those nasty welds

Shoog · 15th September 2007, 08:00 AM

Using MOT's as parafeed chokes in an RH807 amp - works well with no real downsides.
Also using one as a power supply choke, though at 500mA I'm not to certain if its working as a choke or as a big 100R resistor with good power disperation properties. I would guess theres probably just enough inductance left to take care of switching noise.

Shoog

14th September 2007, 02:53 AM	#1
ak_47_boy diyAudio Member Join Date: Sep 2006	MOT's as output transformers? How would a few microwave oven transformers due for output transformers? They have a independence of 2200 ohms with a 8 ohm load. They could do as HV chokes also?

14th September 2007, 03:08 AM	#2
rcavictim diyAudio Member Join Date: Jun 2004 Location: Cool end of a soldering iron NW of Toronto	They work well as chokes. Not so as ouput iron. I thought one might do just what was wanted in a guitar amp...distort. Not even good enough for that application, the HF response is non existant. __________________ I.Q.Test. Have you ever purchased a recreational snowmobile?

14th September 2007, 07:39 AM	#4
rcavictim diyAudio Member Join Date: Jun 2004 Location: Cool end of a soldering iron NW of Toronto	I have used them with success without removing the magnetic shunts (but I agree that you should) in a breadboarded 6080 (several in parallel) parafeed amp. __________________ I.Q.Test. Have you ever purchased a recreational snowmobile?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Difference between SE output transformer and push-pull output transformers	hilbert_mostert	Tubes / Valves	12	8th March 2009 05:10 PM
Help identifying a pair of output transformers and power transformers	mjk130	Parts	3	30th January 2009 10:44 AM
2a3 output transformers....	button_fly	Tubes / Valves	3	10th October 2007 02:05 PM
Output Transformers	eduardio	Tubes / Valves	2	13th May 2005 02:42 PM
Using output transformers on Zen Amp?	G	Pass Labs	14	5th November 2004 11:54 PM

14th September 2007, 06:27 AM	#3
martinab2 diyAudio Member Join Date: Mar 2004 Location: aberdeen, uk	Useless as an output transformer unless you want bass only. Made quite a reasonable (if heavy and bulky) plate choke in a 2a3 parafeed amp. Current limiting shunts are best removed first.

14th September 2007, 02:11 PM	#5
sorenj07 diyAudio Member Join Date: May 2006	Why not just choke-input filter the MOT to get around 1700-1800VDC. Rectify with a couple TV damper diodes? You could probably run some big tubes in SE with that kind of power. Don't MOT's also have filament heaters? p.s. please don't die.

14th September 2007, 10:12 PM	#7
sorenj07 diyAudio Member Join Date: May 2006	you could also cut the core apart and re-wind a new bobbin for it, to make it a choke or more manageable voltage.

14th September 2007, 10:36 PM	#8
ak_47_boy diyAudio Member Join Date: Sep 2006	I would but they are always welded.

14th September 2007, 10:58 PM	#9
Geek diyAudio Member Join Date: Sep 2004	Angle grinder can take care of those nasty welds

15th September 2007, 08:00 AM	#10
Shoog diyAudio Member Join Date: Aug 2002 Location: Eire	Using MOT's as parafeed chokes in an RH807 amp - works well with no real downsides. Also using one as a power supply choke, though at 500mA I'm not to certain if its working as a choke or as a big 100R resistor with good power disperation properties. I would guess theres probably just enough inductance left to take care of switching noise. Shoog

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read