Ok, but i dont get what the next step is. I meassured some things, but what exactly am i going to find out. If i wanna use it for a gainclone, shouldnt i establish the best connection in terms of the input for the gainclone and not what was intended for this old amp (I think it was a 20W amp)??
NO. Try doing a bit of research of how a transformer works. Generally you cannot play around with the primary tappings to get the correct output voltage. A 110V primary is designed to run at 110V, yes you could use less primary voltage but this is not what we are aiming to acieve here.
You have two primaries, the second of which has a few extra turns to enable it to run with a slightly higher voltage.
AndrewX is harping on about a bulb tester, you don't need one just yet, we are still trying to establish the phasing of the primaries.
The bulb tester allows you to safely power up mis-wired primaries.
it is in my view an indispenable tool.
A dual primary or multitapped primary is potentially the most dangerous bit of kit us experimenters can get a hold of.
The bulb tester solves the danger bit.
It even prevents the blown fuse.
it is in my view an indispenable tool.
A dual primary or multitapped primary is potentially the most dangerous bit of kit us experimenters can get a hold of.
The bulb tester solves the danger bit.
It even prevents the blown fuse.
He will need a bulb tester when he first connects it to mains, so best to buy the parts for that now so he is not tempted to try without it when the time comes. Nowadays I would use this even for a brand new transformer from a reliable supplier. So simple, so cheap, and so useful. Also a good test of wiring ability: someone who can't build a safe bulb tester, or requires detailed instructions for it, should not be building mains PSUs.
if you have another small traffo with say 6 volts secondary, things will be easier...
i never used the bulb tester, never needed one, but that is just me...
I think i found the right connections: (I used a 11 volt transformer and meassured output on the Blue-Black)
I tried the following settings.
240: Black-Blue connected/Current on Yellow-Red: Ratio: 13.222
220: Black-Blue connected/Current on Brown-Red: Ratio: 11.55
110: Current on Blue-Red. Ratio: 5.89
130: Current on Black-Yellow. Ratio: 6.91
Could this be the connections for the four inputs. I think it makes sense. It would create an output at:
110: 18.67V
130: 18.81V
220: 18.86V
240: 18.15V
Thanks again
I tried the following settings.
240: Black-Blue connected/Current on Yellow-Red: Ratio: 13.222
220: Black-Blue connected/Current on Brown-Red: Ratio: 11.55
110: Current on Blue-Red. Ratio: 5.89
130: Current on Black-Yellow. Ratio: 6.91
Could this be the connections for the four inputs. I think it makes sense. It would create an output at:
110: 18.67V
130: 18.81V
220: 18.86V
240: 18.15V
Thanks again
Last edited:
And also what VA value do you think it is, anyway i can find out? Big enough to handle a gainclone? It weighs 1726 grams.
Legth: 11cm
Hight: 5cm
With: 8cm
I was thinking about 15-20. Could it then maybe be used in a dual mono amp?
Thanks
Last edited:
Testing the VA rating of the secondaries is difficult to do accurately and several people have their own ways of approximating what the original design was capable of. In the case of a single secondary you can often use the datasheets of other transformers with similar weight to give you some idea. With multiple secondaries it's down to experimentation.
My method is to load up each secondary until the voltage starts to drop, at the same time making sure that the transformer is still running cool. Ultimately the transformer will fail if any winding overheats.
With a transformer designed to provide driver stages with a higher voltage than the output stages, I would start by seeing what the High Current windings can provide. These can normally be spotted by the thicker secondary wires.
My method is to load up each secondary until the voltage starts to drop, at the same time making sure that the transformer is still running cool. Ultimately the transformer will fail if any winding overheats.
With a transformer designed to provide driver stages with a higher voltage than the output stages, I would start by seeing what the High Current windings can provide. These can normally be spotted by the thicker secondary wires.
Last edited:
are these measurements of the iron(not including the coils)?
if it is, and the 1.7 kg weight tells me you have a fairly sized traffo
good enough for a gainclone....
I do not test any transformer without a dim bulb tester. I use to, then 1 day I hooked up 120 to a transformer only to learn it was a choke. I fried my power strip, ruined my simpson analog multi meter and arc flashed my eyes.
My dim bulb tester was 2 feet away.
The same thing can happen if the transformer is shorted.
When I joined this Forum, the dim bulb tester (mains bulb tester) did not seem to ever get mentioned.
I asked how to check that the phasing of a dual primary could be wired up safely.
No one came in to suggest using the bulb tester.
It was some years later that I came across this safe method.
I have championed this safe method ever since.
But it does have limitations.
It cannot be used to adjust the output bias of power amplifier.
It does not protect an amplifier that is currently powered up with the smoothing fully charged and a slipped test probe shorts out a critical pair of traces/joints/device legs.
I asked how to check that the phasing of a dual primary could be wired up safely.
No one came in to suggest using the bulb tester.
It was some years later that I came across this safe method.
I have championed this safe method ever since.
But it does have limitations.
It cannot be used to adjust the output bias of power amplifier.
It does not protect an amplifier that is currently powered up with the smoothing fully charged and a slipped test probe shorts out a critical pair of traces/joints/device legs.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.