I think it is typical for single ended amplifiers. Note that the maximum SE output power readings in the tube datasheets relate to a THD figure of 10 %.
Best regards!
Best regards!
This model requires a high sensitivity speaker to play music. The transformers are small. I had the same problem with a device that came for repair. The feedback resistors cannot correct this level of sound distortion.
Yeah, feedback resistors (and in general all the resistors I checked) are in spec (surprisingly). I replaced a few in the power supply just to make sure. Only one had a problem, the end cap came off, probably heat stressed but it was still measuring in spec.
I did try to measure the output voltage with my DMM but get a few hundred millivolts, almost 1V. I will get out the AC voltmeter today and see what's happening.
I did try to measure the output voltage with my DMM but get a few hundred millivolts, almost 1V. I will get out the AC voltmeter today and see what's happening.
It lives.
One channel is distorted, no idea why, I will wait for the new tubes to show up and investigate further.
In the meantime I will check the volume and tone control pots and associated hardware, maybe give them a clean see if that does anything.
Either way, it turns out the transformers work. I didn't pay attention to see if it is the original transformer that distorts or the one I borrowed from the SAX100, but I am pretty sure the transformers are the same.
I also put my hands on two modern output transformers for PA systems (100V) I will use in the future to rewind some new transformers if need be. These new transformers have the wrong primary impedance but they have identical core cross section and shape and more importantly they have a plastic coil former with proper terminations for the windings.
One channel is distorted, no idea why, I will wait for the new tubes to show up and investigate further.
In the meantime I will check the volume and tone control pots and associated hardware, maybe give them a clean see if that does anything.
Either way, it turns out the transformers work. I didn't pay attention to see if it is the original transformer that distorts or the one I borrowed from the SAX100, but I am pretty sure the transformers are the same.
I also put my hands on two modern output transformers for PA systems (100V) I will use in the future to rewind some new transformers if need be. These new transformers have the wrong primary impedance but they have identical core cross section and shape and more importantly they have a plastic coil former with proper terminations for the windings.
Same here. Just looted a pair of quadruple C cored 100 V line matching trannys of sustantial size (German standard SM74) that are awaiting a rewind for 40 watts OPT's.
Best regards!
Best regards!
Thanks! I'm well aware of Altronics, though, but shipment of heavy goods from Down Under to Germany is expensive, and there aren't double C or quadruple C cores.
Btw, did you know the - now extinct - WWW site that presented a 6CM5/EL36 PP amplifier, even with UL, around the Altronics M-1115 transformer?
Best regards!
Btw, did you know the - now extinct - WWW site that presented a 6CM5/EL36 PP amplifier, even with UL, around the Altronics M-1115 transformer?
Best regards!
Not sure what site it was.
Altronics sold the Currawong amp kit, 6L6 PP with M1115 output trannies. I've got one. You can still get the PCB and all the Silicon chip magazines with the build on the Silicon Chip site.
https://www.radiomuseum.org/r/silicon_currawong_2x10w_rms_stereo_valve_amplifier_kit.html
The trannies are not big and not that heavy. Shouldn't be too much to post overseas. I am pretty sure it is a lot more expensive the other way around.
Altronics sold the Currawong amp kit, 6L6 PP with M1115 output trannies. I've got one. You can still get the PCB and all the Silicon chip magazines with the build on the Silicon Chip site.
https://www.radiomuseum.org/r/silicon_currawong_2x10w_rms_stereo_valve_amplifier_kit.html
The trannies are not big and not that heavy. Shouldn't be too much to post overseas. I am pretty sure it is a lot more expensive the other way around.
These are 100 V line matching transformers, aren't they? So the maximum primary voltage between tabs COM and 1.25 W calculates to 346 V. Is it sufficient?
I'm planning to rewind my SM74 quad C core trannies according to one of Patrick Turner's schemes with a plate to plate impedance of 6400 Ω.
Best regards!
I'm planning to rewind my SM74 quad C core trannies according to one of Patrick Turner's schemes with a plate to plate impedance of 6400 Ω.
Best regards!
I am not sure. I think the primary voltage is designed to be 100V. I wouldn't trust the winding as is to put 300V on it. Measuring impedance it looks like you need to double the primary winding to get to the 5K of the Sansui tranny for instance. The output shows very similar impedance (with the 8Ohm Sansui tranny) on the 1.25W terminals.
Sorry, disregard above post. Got confused.
Yes, they are 100V line matching transformers.
I am not sure the primary winding would take 300V as is.
The output inductance measures similarly with the Sansui trannies on the 8Ohm terminals. The primary inductance on the 1.25W is about half that of the Sansui.
Hope this helps.
Here's some experimental info on the trannies available from Altronics:
https://www.ozvalveamps.org/optrans.htm
Yes, they are 100V line matching transformers.
I am not sure the primary winding would take 300V as is.
The output inductance measures similarly with the Sansui trannies on the 8Ohm terminals. The primary inductance on the 1.25W is about half that of the Sansui.
Hope this helps.
Here's some experimental info on the trannies available from Altronics:
https://www.ozvalveamps.org/optrans.htm
Well, the M-1115 matches loads up to 15 watts to a 100 V line, when the line is connected to COM and 15W. If you apply 100 Vac to these terminals, a voltage of 100 Vac * sqrt (15/1.25) = 346.4 Vac appears between terminals GND and 1.25.
Best regards!
Best regards!
MR niznai ...In response to your first question in this post... I found out the number of turns of the transformer. Why didn't it work for winding?
Oh, thank you very much for that.
I will definitely use your info for winding, I am just not yet ready to do it. I bought the commercial transformers just for the newer hardware (core and formers). They will be rewound to your specs after I go through the receiver and see what else is wrong with it. Right now I am trying to deal with the distortion on one channel. Taking out pots and switches is serious business with this thing.
I will definitely use your info for winding, I am just not yet ready to do it. I bought the commercial transformers just for the newer hardware (core and formers). They will be rewound to your specs after I go through the receiver and see what else is wrong with it. Right now I am trying to deal with the distortion on one channel. Taking out pots and switches is serious business with this thing.
Do you have an oscilloscope?
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Yeah, I have a couple. But I know the switchgear and pots are dirty and they feel rather scratchy too. I will also replace the RCA connectors at the back because they are pitted as hell and also slightly larger than modern cable connectors so you really need to shove them in. I have replaced the speaker connectors to be able to use normal speaker bananas. None of that helps sound quality.
I did briefly scope the signal when I was testing with a 1kHz sinewave from my generator and I found the sound level after the transformer was lower than that out of the output tube plate, but that may be just the higher voltage present at the plate. Didn't actually measure it because the scope I used isn't calibrated. I did however try to turn it up to clipping, which occured at about half the volume but that may be because I was on a dim bulb tester and the voltage at the input transformer didn't get to 100V. This is a Japan voltage unit, runs on 100V. I had at the max about 96V and the current was severely limited with a 60W bulb.
I did briefly scope the signal when I was testing with a 1kHz sinewave from my generator and I found the sound level after the transformer was lower than that out of the output tube plate, but that may be just the higher voltage present at the plate. Didn't actually measure it because the scope I used isn't calibrated. I did however try to turn it up to clipping, which occured at about half the volume but that may be because I was on a dim bulb tester and the voltage at the input transformer didn't get to 100V. This is a Japan voltage unit, runs on 100V. I had at the max about 96V and the current was severely limited with a 60W bulb.
niznai :......did briefly scope the signal when I was testing with a 1kHz sinewave from my generator and I found the sound level after the transformer was lower than that out of the output tube plate, but that may be just the higher voltage present at the plate. Didn't actually measure it because the scope I used isn't calibrated. I did however try to turn it up to clipping
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. does the channel with the most distortion have a ok output choke? Or is it the one with the problem?
.
- conect domi load to 8 ohm outpt terminal in L and R (8 ohm 7 watt sement resistor)
-Apply a 1 kHz sin signal with a 1v p-p... to the input aux L and R . of the faulty channel.
-connect the scope first to the domi load of at the output faulty channel
-. Turn up the volume until the signal starts to distort in output of faulty channel..
- What is the amplitude of the signal in output Before Completely distorted?
-Repeat this test on the ok channel. Here is what the amplitude of the signal before completey distorted ?
-scope shuld be in ac input and x10 probe.
-please take pictures of tow test on scope.
After completing this step, we can continue and the solve cause of the distortion. First, look for abnormal distortion scope.
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. does the channel with the most distortion have a ok output choke? Or is it the one with the problem?
.
- conect domi load to 8 ohm outpt terminal in L and R (8 ohm 7 watt sement resistor)
-Apply a 1 kHz sin signal with a 1v p-p... to the input aux L and R . of the faulty channel.
-connect the scope first to the domi load of at the output faulty channel
-. Turn up the volume until the signal starts to distort in output of faulty channel..
- What is the amplitude of the signal in output Before Completely distorted?
-Repeat this test on the ok channel. Here is what the amplitude of the signal before completey distorted ?
-scope shuld be in ac input and x10 probe.
-please take pictures of tow test on scope.
After completing this step, we can continue and the solve cause of the distortion. First, look for abnormal distortion scope.
Hi hooman, right now both transformers are good, so I don't think that is where the problem lies. I have done exactly what you described but as I said, the scope I used is not calibrated so not sure what the output voltage is. I will clean the pots and switches first and try to check as many resistors as I can and other things and then I will run the test again with a proper AC voltmeter to measure the output at clipping. I managed to change the input RCA connectors last night, so another job ticked off.
Well, cleaned the switchgear and pots and have run another listening session. After a little while on the dim bulb I found no reason not to go to full power.
On the dim bulb I found one of the output tubes was not lit up (or not much, can't tell very well, it has some sort of shielding above the cathode) and on checking I found it was weak, so I replaced it with another unknown tube saved from my stash of dead receivers but this one went very well. The distortion was gone.
So I plugged the receiver into full power (100V, mind you) and attached it to my speakers (Yamaha NS1000). I didn't expect much, but boy oh boy, this thing has left me speechless. I honestly did not expect much from it, but this?!! Wow. I run it through my test tunes to see how it responds and it shines. Of special note was the rendition of Yours is no Disgrace (Yes), which was a new experience for me, like I had never heard it before. I am sure the speakers help a lot, but even my class A (SS) amps did not provide this experience. And all this with what? Maybe 15W or so? Wow.
Oh, and I cam crank it all the way to the max with no distortion and it gets loud enough to annoy my wife. Trannies don't buzz, no hum in the speakers, no unexpected heat, tone controls work, what can I say? I will try to revive the radio section and put it on daily duties.
I am so chuffed right now, I think I am going to revive the other single ended Sansui receiver I have (the SAX-100, which has donated one output transformer for the SM12). Which means rewinding transformers if I do not manage to score some god forsaken NOS trannies from Japan.
On the dim bulb I found one of the output tubes was not lit up (or not much, can't tell very well, it has some sort of shielding above the cathode) and on checking I found it was weak, so I replaced it with another unknown tube saved from my stash of dead receivers but this one went very well. The distortion was gone.
So I plugged the receiver into full power (100V, mind you) and attached it to my speakers (Yamaha NS1000). I didn't expect much, but boy oh boy, this thing has left me speechless. I honestly did not expect much from it, but this?!! Wow. I run it through my test tunes to see how it responds and it shines. Of special note was the rendition of Yours is no Disgrace (Yes), which was a new experience for me, like I had never heard it before. I am sure the speakers help a lot, but even my class A (SS) amps did not provide this experience. And all this with what? Maybe 15W or so? Wow.
Oh, and I cam crank it all the way to the max with no distortion and it gets loud enough to annoy my wife. Trannies don't buzz, no hum in the speakers, no unexpected heat, tone controls work, what can I say? I will try to revive the radio section and put it on daily duties.
I am so chuffed right now, I think I am going to revive the other single ended Sansui receiver I have (the SAX-100, which has donated one output transformer for the SM12). Which means rewinding transformers if I do not manage to score some god forsaken NOS trannies from Japan.