Chinese 6L6 5W amp with toroidal PT?

[leevc5]

Greetings, once again in trouble but this time not with a Hoffman amp. Y'all have saved me before so her I am again looking for help.
Little Chinese amp got for $70 shipped:
http://www.seymourduncan.com/forum/attachment.php?attachmentid=77846&d=1484800228

Only getting 50% voltage reading at J20-J23.
have wired xfmr two red wires to AC +, two black wires to AC return. Have tried separate red/black pairs individually wired to power cord and get same readings. It seems that I need a wiring scheme that runs these black/red pairs in series so I can get sufficient voltage to the board. Any suggestions will be greatly appreciated.

[PRR]

> 50% voltage reading at J20-J23.

Actual Volts on *each* winding numbers, please?

J20 to J21 should be near 260V.

J23 to J22 should be a little over 6V.

[leevc5]

J20 and 21 are ~130 and J22 and 23 ~3 in all three configurations I tried.
Or are you asking for something different?
Think that what is needed is a way to get black/red set one and two wired to the 115V power cord so that tney work in series. Is there a way to do this and if so will it increase the output side of the transformer to the voltage needed at J20-23? Or will it turn the xfmr into smoke and ashes?

[HotBluePlates]

... Think that what is needed is a way to get black/red set one and two wired to the 115V power cord so that tney work in series. ...

Right now you have two 115vac primary windings in series; that's wiring for 230vac from the wall.

You should figure out how those windings are presently hooked up, and place them in parallel.  That will raise your secondary output voltage to the value on the schematic.

[PRR]

> you have two 115vac primary windings in series

I read it as each primary connected to 120V.

"wired xfmr two red wires to AC +, two black wires to AC return.
"tried separate red/black pairs individually wired to power cord and get same"

I am having trouble finding any interpretations other than:

* He has 60V walls (hyper unlikely)

* They wound the PT with two 230V primaries (stupid but possible)

[leevc5]

So, if "stupid but possible" is the case and I have two 230v windings is there anyway I can get the voltage I need out of the output side?

[sluckey]

According to the schematic, you have two 115V windings. Schematic shows them connected in series for 230V operation. But you need to operate from 115V. So...

It's only 4 wires. Disconnect all 4. Then connect one probe of your ohm meter to one wire. Touch the probe to the other three wires, one at a time. Only one should show a resistance reading. Put a piece of tape around those two wires to identify them as one 115V winding. Now verify that the other two wires have resistance. If they do, put a piece of tape around those two wires to identify them as the other 115V winding.

Now connect one wire from each winding together and also connect to the line. Connect the other two wires together and also to the other side of the line. Plug into the wall. If you get the correct voltage you are done. If you get a very low voltage, you need to reverse the two connections of one winding.

[leevc5]

Maybe I did something wrong:
1. checked ohms and found pairs that had readings. Black and red wire set 1 and black and red set 2
2. Connected red wire from set 1 to red wire from set 2 and connected to AC power cord hot
3. Connected black wire from set 1 to black wire from set 2 and connected to AC power cord return.
4. Results were J20-23 50% of required voltage 260V - 6.3V
5. Reversed connections of one winding - took set 1 red and replaced set 1 black and moved set 1 black to replace it. now set 2 red ad set 1 black are connected to AC hot and Set 1 red and set 2 black are connected to AC return.
6 Transformer started smoking when I plugged it in.
     What am I doing wrong?

Maybe I need two power cords, one for each winding?

[HotBluePlates]

Maybe I did something wrong:
1. checked ohms and found pairs that had readings. Black and red wire set 1 and black and red set 2
2. Connected red wire from set 1 to red wire from set 2 and connected to AC power cord hot
3. Connected black wire from set 1 to black wire from set 2 and connected to AC power cord return.
4. Results were J20-23 50% of required voltage 260V - 6.3V

 
So you wired up this amp?  What you described here is connecting the primaries in parallel, and you have too-little output voltage.  If that is the case, you'd then connect them in series.
 

...
5. Reversed connections of one winding - took set 1 red and replaced set 1 black and moved set 1 black to replace it. now set 2 red ad set 1 black are connected to AC hot and Set 1 red and set 2 black are connected to AC return.
6 Transformer started smoking when I plugged it in.
     What am I doing wrong? ...

You now have the 2 primaries anti-phase, and fighting each other (assuming no other short-circuiting).   

Series:  A.C. --> Red Pri 1  ---- Blk Pri 1 ---> Red Pri 2 ----- Blk Pri 2 ---> A.C.

[PRR]

> primaries in parallel, and you have too-little output voltage.  If that is the case, you'd then connect them in series.

Series on the primary would give half-voltage on the secondaries. No?

As he has tried all else, let's try primary in series, sure.

A really funny thing is: the primaries are shown series but with what sure looks like a US-type plug.

I still would like to know "134V and 6.7V" rather than "50%". Also that the meter has been checked today.

You link to a Seymor Duncan site but SD does not sell this kit? Where did you get it from?

[drgonzonm]

smoking transformer, you need to check other components in the amp. 
I took the opportunity to read the forum in the seymourduncun website, The information provided on this forum was previously provided on this forum with one possible exception.  On the other forum it was suggested only one primary be wired, not both.  pull the tubes, and use a lamp limiter, run the pt only one set of primaries. 

I would like add the following recommendations, some can be dangerous,
0.  When in doubt read the manual. 
1. If you can find data on the pt, then follow it up. verify that it is pt that has 120v primaries, if not;
2. verify that neither the neutral or hot is wired to the chassis.  Make an adapter to feed the amp 240 volts, using your stove, dryer receptacle  etc as your power.  Also verify by reading your meter that power input into your abode is two legs of 120, and it has 240/120v meter.  You might find your power is 208/120v, and the rules change a little bit. 
3.  Replace the pt with the correct value. 

As stated, it is possible that this pt primaries are 230-240 volt

[leevc5]

> primaries in parallel, and you have too-little output voltage.  If that is the case, you'd then connect them in series.

Series on the primary would give half-voltage on the secondaries. No?

As he has tried all else, let's try primary in series, sure.

A really funny thing is: the primaries are shown series but with what sure looks like a US-type plug.

I still would like to know "134V and 6.7V" rather than "50%". Also that the meter has been checked today.

You link to a Seymor Duncan site but SD does not sell this kit? Where did you get it from?

Checked with two different meters. Readings were 150V J20/21 and 3 for J22/23.

[HotBluePlates]

> primaries in parallel, and you have too-little output voltage.  If that is the case, you'd then connect them in series.

Series on the primary would give half-voltage on the secondaries. No?

As he has tried all else, let's try primary in series, sure.

A really funny thing is: the primaries are shown series but with what sure looks like a US-type plug. ...

I don't know for-sure what he's got.  "KLD GT5" is a series of amps, even if this is just a GT5E-variant.

I know I don't trust Chinese documentation.  I trust their build quality even less.

You are right though... If he already tried parallel wired primaries, series wiring would only give less output voltage.

[leevc5]

> primaries in parallel, and you have too-little output voltage.  If that is the case, you'd then connect them in series.

Series on the primary would give half-voltage on the secondaries. No?

As he has tried all else, let's try primary in series, sure.

A really funny thing is: the primaries are shown series but with what sure looks like a US-type plug. ...

I don't know for-sure what he's got.  "KLD GT5" is a series of amps, even if this is just a GT5E-variant.

I know I don't trust Chinese documentation.  I trust their build quality even less.

You are right though... If he already tried parallel wired primaries, series wiring would only give less output voltage.

Eh, so I have a $70 Chinese junk on my hands...might it be worth buying a PT from Hoffman, I think they have on with close to 6.3 and 260 output or just try and get my money back?

{EDIT - untangled quote -PRR}

[HotBluePlates]

Sorry... It seems my frustration earlier was simply because I didn't slow down to understand all of what you said re: testing with the PT.

As I see it (while still not actually seeing the amp), buying another PT may be problematic because you'll need to sort out mounting issues for any non-toroid PT, as well as for any toroid which is not the same physical size.

The closest Hoffman match seems to be the MOJO779 for Reverb Units, but it's $52 plus shipping.  No guarantee the heater or B+ will support 6L6 (Hoffman's hookup info doesn't have the spec for current, and neither does Mojo's website).

[leevc5]

Sorry... It seems my frustration earlier was simply because I didn't slow down to understand all of what you said re: testing with the PT.

As I see it (while still not actually seeing the amp), buying another PT may be problematic because you'll need to sort out mounting issues for any non-toroid PT, as well as for any toroid which is not the same physical size.

The closest Hoffman match seems to be the MOJO779 for Reverb Units, but it's $52 plus shipping.  No guarantee the heater or B+ will support 6L6 (Hoffman's hookup info doesn't have the spec for current, and neither does Mojo's website).

022772 PT should work but don't want to throw money at this thing. Probably just end up going through the painful process of trying to return and get refund...never to buy Chinese again unless through a third party like Epiphone....

[PRR]

Alternates are to move to Europe/UK/China, or get a 115V-230V converter.

This should work electrically; mechanical fit has to be checked:
Transformer - Hammond 261G6, Plate & Filament or Bias, 250V@130mA
Primary: 115 VAC, 125 VAC, 60 Hz.
Secondary #1: 250 VCT @ 130 mA
Filament Secondary #2  6.3 V @ 2 A
Mounting Centers  3.56" u-bracket
Weight   2 lbs.
Price: $42.32  here SKU: P-T261G6 Item ID: 003508
Price: $37.79 here

[leevc5]

Thank you again PRR. Have an old champ PT in a box somewhere, maybe givemit a try:
https://www.tedweber.com/media/import/w022772sch.JPG

[HotBluePlates]

Thank you again PRR. Have an old champ PT in a box somewhere, maybe givemit a try:
https://www.tedweber.com/media/import/w022772sch.JPG

Not that transformer requires a different type of rectifier ('full-wave' instead of 'full-wave bridge') and may result in enough B+ to exceed the ratings of your filter caps (assuming KLD used the 450v rated caps they have drawn on the schematic).

If you did use it, the 125vac primary (BLK, BLU) and the 300-0-300vac secondary (RED/WHT) are probably your best choice.

[leevc5]

Thank you for steering away from what would have been a catastrophic mistake.

[drgonzonm]

You can find a toriod transformer with almost the same primaries and secondaries at ampmaker.com 240/120 input.  or you can select one that provides a mulitple choice b+

[leevc5]

The Chinese had no clue about how to get the thing to work. They told me to send it back, for a full refund, they want to use it to train their workers how to troubleshoot amps. Through it in a box and sent on back to China. Still want a SE 6L6 amp but not going to look to China anymore. There has to be something in the good old USA.

[drgonzonm]

The Chinese had no clue about how to get the thing to work. They told me to send it back, for a full refund, they want to use it to train their workers how to troubleshoot amps. Through it in a box and sent on back to China. Still want a SE 6L6 amp but not going to look to China anymore. There has to be something in the good old USA.

Look at ampmaker.com.  Source their PT and build your own.