PT Identification

[Ed_Chambley]

Here are the specs I have from testing unloaded.  I have had this for years and am considering a bass amp build.  Problem is I do not know the current and there is no numbers on the part.
Power Transformer - 870 VAC CT  (435 - 0 -   435)
6.3V  Heater Winding
5V Rectifier Winding
25VAC CT Bias Winding
Size:  5.0 x 4.0 x 4.75 Height
Mounting holes: 3.5 x 3.0 inches
Core size: 4.5 x 3.75 x 2.25 in.
Weighs 14lbs.

Anyway to test ma?  Anyone recognize?  I found it in the box at an old TV and Amp repair shop, but the only thing I could make out on the box was the postmark from 1958.

[DummyLoad]

are you sure about the weight? any markings on it at all?

the closest thing i can find that is similar in size and voltage ratings is the hammond 278CX - 12.5Lb and 3 x 3.81 mtg. ctr. it carried a 460mA @ 800VCT rating - i'd take a SWAG and say it's around 400-500VA

i'd build a 200W bass amp with that thing without hesitation or reservation.

post the resistance readings of all the windings and we can zero in a bit closer. 

--DL

[TIMBO]

PAGING Dr. Dummy  I too have an unidentified PT that needs a DIAGNOSIS and all i've got to go by is the HT is 285-0-285,5v@2A and 6.3v@3A made by Henderson (in Australia)and weighing at a possible 1-2 lbs. So what do you think DOC?????

[Ed_Chambley]

are you sure about the weight? any markings on it at all?

the closest thing i can find that is similar in size and voltage ratings is the hammond 278CX - 12.5Lb and 3 x 3.81 mtg. ctr. it carried a 460mA @ 800VCT rating - i'd take a SWAG and say it's around 400-500VA

i'd build a 200W bass amp with that thing without hesitation or reservation.

post the resistance readings of all the windings and we can zero in a bit closer. 

--DL

Thanks for the input.  I get some readings.  It may not weigh 14, it could be less, I did not weigh it with a postage scale or anything like that.

[DummyLoad]

So what do you think DOC?????

doorstop?    

--DL

[TIMBO]

Thanks, that work well

[DummyLoad]

Thanks, that work well

srsly. post some resistance measurements and core size and we can estimate it's capabilities. you can make a correlation with other transformers with known values that are similar.

--DL

[PRR]

> a possible 1-2 lbs

I have a lobster and it weighs a possible 1-2 lbs. What is it worth?

I have a bag of weed and it weighs a possible 1-2 lbs. What is it worth?

Not enough information. A 1-pound lobster is a nice meal. A 2-pound lobster is gluttony.

Throw it on the baby-scale, then compare to other similar lumps.

[TIMBO]

This is what i have, The laminates are 3.5"x 4"x 1" ,weights 4lb (so i was close) is 285-0-285 and measures 500ohms between the two HTs. I look at hammond for a close match but nothing but close is 275-0-275 @ 125mA weighing 4.2lb. So i would think it might be around 90-100mA as it was the tubes it was pushing totaled 70mA and it also had a radio in the circuit as well(radio/record player).Thanks

[DummyLoad]

So i would think it might be around 90-100mA

that's what i'd call it too - 90mA to be conservative given the higher secondary DCR than the hammonds. another useful piece of information is the unloaded voltage with the rated primary voltage applied. use duncan munroe's PSU designer and you'll get a very close approximation by simulation.

--DL

[Ed_Chambley]

My vision is getting very bad.  I found the numbers on the PT and the only thing I found is a reference to zeneth.

The number is-343pf-583

There is another number I assume is the SN-839748

Still haven't gotten resistance reading yet, but will very soon.

[PRR]

> weights 4lb

4 pound lobster feeds the whole family.

And BTW: the 5V 2A points to 5Y3 rect, so a pair of 6V6 not a pair of hard-worked 6L6.

> the tubes it was pushing

You know the tubes?? Then you know the design load, near-enuff.

If you kept the OT also, and used similar-size power tubes, you have the entire power budget already figured out professionally. 6F6 6V6 EL84 to taste (they are similar-enough on power ability), add the driver and preamp of your choice.

[PRR]

> The number is-343pf-583

Google that number, you find three hits about transformers:

http://www.worthpoint.com/worthopedia/vintage-zenith-power-transformer-6l6-162311519

http://www.ebay.com/itm/Vintage-Gulbransen-Organ-Tube-Amplifier-APS-5-/290579183900

http://www.ebay.com/itm/Vintage-Transformer-Iron-Parts-For-DIY-tube-Amplifiers-Preamplifier-Projects-/290616509891

Two of these suggest it came from an organ (good stuff) and boasted a 5U4 and a pair of 6L6, plus some 12AU7. Sounds like geetar feed to me.

[TIMBO]

Thanks guy's, The original lineup in the amp side was 1x6aq5 and 1x6av6. So my thoughts were 2x6v6 and 2-3 12ax7 (Stout,2204).Thanks again 

[Ed_Chambley]

> The number is-343pf-583

Google that number, you find three hits about transformers:

http://www.worthpoint.com/worthopedia/vintage-zenith-power-transformer-6l6-162311519

http://www.ebay.com/itm/Vintage-Gulbransen-Organ-Tube-Amplifier-APS-5-/290579183900

http://www.ebay.com/itm/Vintage-Transformer-Iron-Parts-For-DIY-tube-Amplifiers-Preamplifier-Projects-/290616509891

Two of these suggest it came from an organ (good stuff) and boasted a 5U4 and a pair of 6L6, plus some 12AU7. Sounds like geetar feed to me.

Yep, found the same thing.  This is not a pull, it is new.  Never been installed.  I need to figure out if it will run 6, 6550 and a couple of 12AX7's.  Wanting to build an ampeg inspired bass amp because ampeg bass amps are the only tube bass amp I am familiar with.  Looking at it you would think it would do it with no problem as it is massive and heavy.

[PRR]

> if it will run 6, 6550

I read it as two 6L6. Say 35-55 Watts output.

Six 6550?? Well yeah, it can "run" if you under-load it to make about the same power as the pair of 6L6. (Use 6.6KCT load for all 3 pair, not 1.6K like you might for the 270 Watts this PT won't support.) And add a heater transformer for the extra 8 Amps.

[plexi50]

> a possible 1-2 lbs

I have a lobster and it weighs a possible 1-2 lbs. What is it worth?

I have a bag of weed and it weighs a possible 1-2 lbs. What is it worth?

Not enough information. A 1-pound lobster is a nice meal. A 2-pound lobster is gluttony.

Throw it on the baby-scale, then compare to other similar lumps.

  Can i have all three or do i have to make a choice? Ive seen that transformer before but cant remember what i pulled it from. Mine looked like a laminated iron Zebra. Whats that?

[Ed_Chambley]

> if it will run 6, 6550

I read it as two 6L6. Say 35-55 Watts output.

Six 6550?? Well yeah, it can "run" if you under-load it to make about the same power as the pair of 6L6. (Use 6.6KCT load for all 3 pair, not 1.6K like you might for the 270 Watts this PT won't support.) And add a heater transformer for the extra 8 Amps.

I get what you're puttin' down.   The ad for the one that sold "Worthpoint" is the only place where I can find out any information about tube lineup.  It looks like it is way overkill for 2 power tubes.  I am not certain what the loaded voltages will be, but I am not familiar with a 2, 6L6 PT thats HT 435-0-435.  Do you know of an amp that uses 2, 6L6's with a PT with this much voltage?  The physical size and weight has me puzzled.  Still have not gotten resistance readings, but I will as it only takes a few minutes to do.  I just need a few minutes to do it.

[Ed_Chambley]

> a possible 1-2 lbs

I have a lobster and it weighs a possible 1-2 lbs. What is it worth?

I have a bag of weed and it weighs a possible 1-2 lbs. What is it worth?

Not enough information. A 1-pound lobster is a nice meal. A 2-pound lobster is gluttony.

Throw it on the baby-scale, then compare to other similar lumps.

  Can i have all three or do i have to make a choice? Ive seen that transformer before but cant remember what i pulled it from. Mine looked like a laminated iron Zebra. Whats that?

Have all 3.  Why not?  I posted the photos to show the wire colors and the bell covers.  I have never seen one that looks like it, but we know it does not look like your iron Zebra!  When you power up the Zebra, does it run away from you and you have to wait until it gets hungry to come home?

[PRR]

> not familiar with a 2, 6L6 PT thats HT 435-0-435

Ah, yes. Sand-diode makes 600+V which is mighty high for 6L6 even GC. 5U4 gives 480V which is still pretty high.

It seems to be an ORGAN transformer. Organs sell to churches. Churches who buy organs have some money. Churches like their stuff to last a looooong time. Church organs never move, weight is good not bad. So some church organs use *choke input* power supplies. They cost and weigh more, but abuse the rectifier and capacitor less. With 5U4 to choke-input you get right about 360V. This is a sweet zone for old 6L6.

This choke has to be BIG, not the smoothing chokes we find in guitars. It may typically be half the size of the PT. I assume you didn't find it.

You could try to find 8K-10KCT OT at 70 watts or so, run a pair of 6550/KT88.

Resistances might be nice but it takes more than "a few minutes" to suss out what they imply so it may take a while or longer.

[Ed_Chambley]

> not familiar with a 2, 6L6 PT thats HT 435-0-435

Ah, yes. Sand-diode makes 600+V which is mighty high for 6L6 even GC. 5U4 gives 480V which is still pretty high.

It seems to be an ORGAN transformer. Organs sell to churches. Churches who buy organs have some money. Churches like their stuff to last a looooong time. Church organs never move, weight is good not bad. So some church organs use *choke input* power supplies. They cost and weigh more, but abuse the rectifier and capacitor less. With 5U4 to choke-input you get right about 360V. This is a sweet zone for old 6L6.

This choke has to be BIG, not the smoothing chokes we find in guitars. It may typically be half the size of the PT. I assume you didn't find it.

You could try to find 8K-10KCT OT at 70 watts or so, run a pair of 6550/KT88.

Resistances might be nice but it takes more than "a few minutes" to suss out what they imply so it may take a while or longer.

I did find a choke as well, but I don't know if they have anything to do with each other.  It is basically a Hammond 194C.  40 Henries @ 50ma.  It is about half the size of a 270 series Hammond PT.

Not sure what a 40 henries choke would be used for?  Bet you know.

[sluckey]

It is basically a Hammond 194C.  40 Henries @ 50ma.

That's too light weight for PRR's suggestion of choke input power supply. You would need something like the Hammond 193 series, ie, 10H @ 500ma.

[Ed_Chambley]

> not familiar with a 2, 6L6 PT thats HT 435-0-435

Ah, yes. Sand-diode makes 600+V which is mighty high for 6L6 even GC. 5U4 gives 480V which is still pretty high.

It seems to be an ORGAN transformer. Organs sell to churches. Churches who buy organs have some money. Churches like their stuff to last a looooong time. Church organs never move, weight is good not bad. So some church organs use *choke input* power supplies. They cost and weigh more, but abuse the rectifier and capacitor less. With 5U4 to choke-input you get right about 360V. This is a sweet zone for old 6L6.

This choke has to be BIG, not the smoothing chokes we find in guitars. It may typically be half the size of the PT. I assume you didn't find it.

You could try to find 8K-10KCT OT at 70 watts or so, run a pair of 6550/KT88.

Resistances might be nice but it takes more than "a few minutes" to suss out what they imply so it may take a while or longer.

The transformer and me have not been in the same place long enough to get resistance readings, but I will tomorrow.  You mentioned a 5U4 delivering 480vdc.  Did you consider the load of a pair of KT88?  I forget what amp, but some boutique builder is selling a 2/KT88 with 1 12 and states 85 watts.  I gave one a test drive and it was a very nice amp to play with a ES335.  I have sort of had my mind on this since I played it.  It may be a Dirty Dog, just cannot remember.  I will find out.

EDIT: The dual KT88 is a Redplate is a Black Verb Duo.  Specs state 80 watts.

http://redamps.com/blackverbduo/

It is a very nice sounding amp.  It has a lot of bells and whistles, but it doesn't have to be cranked to have a great tone.

[jazbo8]

Check out Rod Elliot's article and download the software to get all the parameters for any transformer >> http://sound.westhost.com/articles/xfmr3.htm

Jaz

[Ed_Chambley]

Check out Rod Elliot's article and download the software to get all the parameters for any transformer >> http://sound.westhost.com/articles/xfmr3.htm

Jaz

Will do, Thanks.

[Ed_Chambley]

I attempted the link information provided and downloaded the different calculation software, but I just do not understand enough about Transformers to fill in the blanks so to speak.

I did measure resistances.
Primary-.8 ohms
Secondary  HT to HT-122.5 ohms
Ht to Ct- 62.7 / 60
Bias Winding, heater and 5v all zero.
Measured with Fluke 79

Not sure if this is all the info needed.  Let me know what else is needed as I would like to understand how to determine the specs of an unknown PT.

[jojokeo]

Isn't there a way to apply a varying load on the thing and get a more educated guess when it starts loading down by X % amount of unloaded voltage reading and then take a current reading at this point also?

If not, then I'd build a more conservative project with it knowing you should be fine and operating on the cool & reliable side of things. For an ambitious project with 6 power tubes you'd be better off using something with known values w/out guesswork. That's a lot of money and time you'd have invested based on a very important unknown. OR, at least make provisions w/ the chassis & parts' locations so that you could un-install the unknown tranny (if it didn't work out) for the one you'd have to buy to make it work properly later so you could at least cover your ass either way.

[Ed_Chambley]

Isn't there a way to apply a varying load on the thing and get a more educated guess when it starts loading down by X % amount of unloaded voltage reading and then take a current reading at this point also?

If not, then I'd build a more conservative project with it knowing you should be fine and operating on the cool & reliable side of things. For an ambitious project with 6 power tubes you'd be better off using something with known values w/out guesswork. That's a lot of money and time you'd have invested based on a very important unknown. OR, at least make provisions w/ the chassis & parts' locations so that you could un-install the unknown tranny (if it didn't work out) for the one you'd have to buy to make it work properly later so you could at least cover your ass either way.

Good suggestion.  I am not going to use 6 power tubes anyway.  I am probably just going to make a KT88, 2 tubes and see where the PT is.  I decided to make a preamp for bass and use it to feed a SS amp per PRR's and others suggestions.  OTOH, I think I would like to attempt an amp based on KT88.  I have been looking at a few and they interest me.

[jazbo8]

I attempted the link information provided and downloaded the different calculation software, but I just do not understand enough about Transformers to fill in the blanks so to speak.

I did measure resistances.
Primary-.8 ohms
Secondary  HT to HT-122.5 ohms
Ht to Ct- 62.7 / 60
Bias Winding, heater and 5v all zero.
Measured with Fluke 79

Not sure if this is all the info needed.  Let me know what else is needed as I would like to understand how to determine the specs of an unknown PT.

Did you click on the labels in the "XFORMER" app (which one are you using)? There are directions on how to measure the required parameters, e.g., http://sound.westhost.com/articles/xfmr3-f4.gif

I think the key is to measure very low resistance of the windings as well as the impedance...

Jaz

[Ed_Chambley]

I attempted the link information provided and downloaded the different calculation software, but I just do not understand enough about Transformers to fill in the blanks so to speak.

I did measure resistances.
Primary-.8 ohms
Secondary  HT to HT-122.5 ohms
Ht to Ct- 62.7 / 60
Bias Winding, heater and 5v all zero.
Measured with Fluke 79

Not sure if this is all the info needed.  Let me know what else is needed as I would like to understand how to determine the specs of an unknown PT.

Did you click on the labels in the "XFORMER" app (which one are you using)? There are directions on how to measure the required parameters, e.g., http://sound.westhost.com/articles/xfmr3-f4.gif

I think the key is to measure very low resistance of the windings as well as the impedance...

Jaz

I looked at all 3.  One is a excel file.  The third one seems like a transformer design tool.  I will check the xformer app closer and do some more reading on it.  If I spend more time with it I may understand it better.

Thanks.

[jazbo8]

I think the first app (XFORMER) is the one you want, click on the field labels on the left side and some of them will bring up a help file showing the test/measurement setup, then follow the direction to obtain the parameter needed.

[DummyLoad]

with the winding resistances resistance readings and the off-load voltage you posted; with SSR, full wave, PSU designer2 states you'll be able to deliver 540V into a 200mA load, or 500V into a 400mA load or, 460V into a 600mA load.  with 870VCT no-load, i'm assuming it's a 800VCT part at a some current rating. so 1.414 * 400V is 565V.

PRR says run a single pair of 6L6GC. he has much more experience than i do. listen to him. i'm a hacker... i'd push it.

--DL

[PRR]

> or, 460V into a 600mA load

And 615V at zero mA load?

615V-460V is 155V lost inside the transformer. At 600mA, that's 93 Watts (right?) of dropped power and heat inside the transformer.

IMHO it is not big enough to have 100 Watts of heat inside for long periods.

10%-15% sag is more reasonable. 615V drops to 553V or 522V. Per your calcs, maybe 180mA-300mA.

522V at 300mA is 156 Watts of DC available. Taking amp efficiency as 50%, that's 78 Watts out and 2 * 39 Watts of plate dissipation.

[HotBluePlates]

So what's the best way to rig this thing for real-world testing?

Hook it up to a rectifier (5U4GB), a filter cap and some 100w resistors as a dummy load? Should Ed just try different resistances to see how much current he can draw before the HT sags?

I ask cause I've only pulled transformers from equipment where the exact ratings were either known, or where I used the transformer exactly the way it was used originally (no calculation/guess involved).

[HotBluePlates]

I think I answered my own question.

The Fun with Tubes website has a Load Box Project which appears suitable for such testing.

As always, you have to be 10% smarter than the equipment you're working with, and make some smart assumptions and careful choices when connecting an unknown to be evaluated with the load box.

[kagliostro]

The Fun with Tubes website has a Load Box Project which appears suitable for such testing.

Nice found HotBluePlates really well build

I never imagined someone had built something like that

----

for those who want to complicate their lives an electronic adjustable dummy load

Schematic


The whole project (with a more readable schematic)
http://www.chirio.com/electronic_load.htm

Mod to use the Dummy Load with B+ voltage levels

I asked to the author and he told me that is possible to use the project also for HV till 800v
the required mods are:
1)potentiometer R2 = 500k
2)max current at 1A is obtained changing the value of  R8 at 0.4R
3)change the model of mosfet with one that can afford 800v
4)use 4 paralleled mosfet as to support the dissipation in heat

K

[PRR]

> complicate their lives an electronic adjustable dummy

For most purposes, a collection of high-power resistors do the same thing, *simple*.

Idle: big amps usually idle 400V-500V at 50mA or 100mA. 500V/50mA is 10K at 25 Watts.

POWER: half the OT p-p impedance, double the expected Wattage. 5F6a Bassman runs 4Kpp OT and makes 40 Watts. Use a 2K 80 Watt resistor.

Resistors are rated for steady power. Power supply sag is quick. If *you* (and your meter) are quick, you can dump 80 Watts into a 50W resistor for several seconds, long enough to read a meter then shut-down.

You may also want to know if an unknown PT can handle a load all-night. Then you want resistors rated higher than the expected/calculated DC Power. And a fire-proof area to test in, and time to keep an eye (and nose) on it for several hours.

It is not pleasant to power-test the supply for a 2*180 Watt amp in summertime.

[DummyLoad]

It is not pleasant to power-test the supply for a 2*180 Watt amp in summertime.

you did, didn't ya... 

--pete