scott2000
Well-known member
Awesome..... Thanks!
Do you have the power supply and Sat stage???? I think that's where the questions are??
Do you have the power supply and Sat stage???? I think that's where the questions are??
Mindprint overheating !
- Thread starter yekuku
- Start date
Help Support GroupDIY Audio Forum:
These are complete schematics, including PSU and SAT parts.
I'm not sure if they are the right revision, as I don't know the difference between the S2 and previous model.
I've also uploaded the schematics for the DTC (Dual Tube Channel) and the En-Vision channelstrip.
I'm not sure if they are the right revision, as I don't know the difference between the S2 and previous model.
I've also uploaded the schematics for the DTC (Dual Tube Channel) and the En-Vision channelstrip.
scott2000
Well-known member
Looks like the En Voice may have the same deal going on with the tube stage and smaller transformer.??....
This should be very helpful for this issue I'd imagine if that's the case....Very cool! Thanks! That's a lot of info...
Edit...It's a bit different..... Wonder what the values are of all those hot resistors???It also Looks like they should've been 1watt to start with but I need to check if the topic said they were replaced from some other wattage ???? ...
R167 and R192 aren't the plate resistors????....It's probably those two red ones on the vertical board edge...??..
This should be very helpful for this issue I'd imagine if that's the case....Very cool! Thanks! That's a lot of info...
Edit...It's a bit different..... Wonder what the values are of all those hot resistors???It also Looks like they should've been 1watt to start with but I need to check if the topic said they were replaced from some other wattage ???? ...
R167 and R192 aren't the plate resistors????....It's probably those two red ones on the vertical board edge...??..
Thank you very much Cyrano , I deeply appreciate it 
If I can be any help to you, please feel free to let me know.
I am downloading them right now , after so much guessing they will certainly be an interesting read
EDIT : Unbelievable ! Scott2000 is right, at the schematics all the burned resistors ( R142,R162,R166,R191,R167,R192) are rated 1 wattbut on the unit they installed 1/4 watt, weird or what ?
The same problem applies on the EnVoice MkI, and it looks like the DTC has the same PSU!
From what I am hearing they redesigned the PSU on the envoice mk2, I would be curious to see what they changed.
I dont want to be greedy here so please forgive my asking , just out f curiosity, Cyrano do you have also the schematics of the envoice mk2?
EDIT2: By looking at the schematics, I think that Monte McGuire is right about the tubes.
Have a look at the attached PSU schematics
If the trafo was the problem then only R142 & R162 should be affected / burned.
The other burned resistors are responsible for the tubes pre-heating (12.6V), maybe the tubes become power hungry and they are loading down the PSU? But then the unit looks to work as expected, the tubes have an impact to the sound.....
Well I dont know, I should wait for the trafo and the new tubes to arrive in order to do some further testing.
You guys rock ! thanks for everything
If I can be any help to you, please feel free to let me know. I am downloading them right now , after so much guessing they will certainly be an interesting read
EDIT : Unbelievable ! Scott2000 is right, at the schematics all the burned resistors ( R142,R162,R166,R191,R167,R192) are rated 1 watt
The same problem applies on the EnVoice MkI, and it looks like the DTC has the same PSU!
From what I am hearing they redesigned the PSU on the envoice mk2, I would be curious to see what they changed.
I dont want to be greedy here so please forgive my asking , just out f curiosity, Cyrano do you have also the schematics of the envoice mk2?
EDIT2: By looking at the schematics, I think that Monte McGuire is right about the tubes.
Have a look at the attached PSU schematics
If the trafo was the problem then only R142 & R162 should be affected / burned.
The other burned resistors are responsible for the tubes pre-heating (12.6V), maybe the tubes become power hungry and they are loading down the PSU? But then the unit looks to work as expected, the tubes have an impact to the sound.....
Well I dont know, I should wait for the trafo and the new tubes to arrive in order to do some further testing.
You guys rock ! thanks for everything
Attachments
scott2000
Well-known member
yekuku said:
Hey! :'(...lol
yekuku said:
Are you sure??? Sometimes the sizes can be misleading..... For example, those little red ones are probably rated higher than we may think...
What are the values of the red ones in your pic on the vertical card next to the tubes????
Hi Scott,
Sorry my bad, I assumed that they were 1/4 Watt based on their sizes , I did not know that you can have increased wattage in small packages.
The red ones on the tube card are the same type and color like the ones that i have replaced .
They are R148 and R218 ( 82k & 100k respectively) and on the schematics they are rated 1 watt just like the others.
Do you think that the red resistors are rated 1 Watt ?
Sorry my bad, I assumed that they were 1/4 Watt based on their sizes , I did not know that you can have increased wattage in small packages.
The red ones on the tube card are the same type and color like the ones that i have replaced .
They are R148 and R218 ( 82k & 100k respectively) and on the schematics they are rated 1 watt just like the others.
Do you think that the red resistors are rated 1 Watt ?
Attachments
scott2000
Well-known member
yekuku said:
Yes...Those are your tube's plate resistors I think...I'd have to look again but sounds right
I think those are Dale Pro resistors....very small package but rated high...The 2 watt ones look like regular half watt....
PR02000201003JR500, etc...
Hopefully you got the values right when you swapped them???sometimes the colors can be tricky if you go off off that thinking your values are skewed when measuring........ You pretty sure you got them right???
I'll need some time for the MKII schematics, I'm afraid. I was sure I had all Mindprint schematics in my repository, but they're not. I'll have to mine the archives.
There's something else that's weird. One of the schematics in that folder is for a Kemper Digital, but seems to have the same style and numbering as the Mindprint ones. Now, I've downloaded these in April 2010, so I can't remember what went on way back then.
Is there any relation between Mindprint and Kemper Digital? Both are German, but Mindprint ceased operations about a year ago. And now the domain kemper-digital.com redirects to kempermusic.com. Shifting again?
There's something else that's weird. One of the schematics in that folder is for a Kemper Digital, but seems to have the same style and numbering as the Mindprint ones. Now, I've downloaded these in April 2010, so I can't remember what went on way back then.
Is there any relation between Mindprint and Kemper Digital? Both are German, but Mindprint ceased operations about a year ago. And now the domain kemper-digital.com redirects to kempermusic.com. Shifting again?
Dale pro ? Well you learn new things everyday ! No worries about the resistors , they are the right valuescott2000 said:
No worries about the schematics, I was just curious to see what they changed in the mk2 PSU.cyrano said:
Thanks for the info, I had no Idea about all these companies, I have mailed mindprint but I got no reply.
scott2000
Well-known member
Well you say everything is working so, it's probably moot to check through some components.... Those blue phillips electros like to poop out after a while from my experience...... those Jumper resistors sometimes are suspect too but, not sure if one going open wouldn't create noticeable issues....
Can't we put an ammeter somewhere and check the current????? I'm asking..... Should be ok with a multimeter???
Can't we put an ammeter somewhere and check the current????? I'm asking..... Should be ok with a multimeter???
Hi Scott,
I have removed the trafo, since the secondary winding has problems and I am hesitating to put it back in order to take measurements.
I have ordered a custom trafo along with 2 new tubes, hopefully I will be able to check the current by the end of this week.
I ll keep you updated as soon as I have the parts in my hands
I have removed the trafo, since the secondary winding has problems and I am hesitating to put it back in order to take measurements.
I have ordered a custom trafo along with 2 new tubes, hopefully I will be able to check the current by the end of this week.
I ll keep you updated as soon as I have the parts in my hands
Urgent question:
I contacted the guy that I have ordered the custom transformer, asking him if we can have a tight tolerance concerning the output of the trafo (250V)
He does not have great experience in step up trafos, as he mostly manufacture step down, and he wants to know how much volts the trafo should output with no load.
So the question is to you all transformer experts out there :
When using a 2-3VA step up trafo ( Primary 15V- Secondary 250V) and feeding exactly 15V, how many volts should the secondary output without any load ?
I guessed that about 260V should be ok, but the guy told me that these small transformers usually have a lot of drop in voltage when load is connected.
Any ideas ? Anyway I can calculate this ?
I contacted the guy that I have ordered the custom transformer, asking him if we can have a tight tolerance concerning the output of the trafo (250V)
He does not have great experience in step up trafos, as he mostly manufacture step down, and he wants to know how much volts the trafo should output with no load.
So the question is to you all transformer experts out there :
When using a 2-3VA step up trafo ( Primary 15V- Secondary 250V) and feeding exactly 15V, how many volts should the secondary output without any load ?
I guessed that about 260V should be ok, but the guy told me that these small transformers usually have a lot of drop in voltage when load is connected.
Any ideas ? Anyway I can calculate this ?
scott2000
Well-known member
Maybe start another thread discussing this...... Just in case nobody checks this one out..... Make it catchy... like urgent! Transformer info needed...... or something......
May catch a big one.... ;D
May catch a big one.... ;D
I'm almost sure that this is NOT made as a step-up transformer, but rather a off-the-shelf standard 230:15V (or something like that, maybe 12V) transformer which's main property is the cost.
If it was custom-made, it would be MUCH cheaper to make it either as another winding on primatry trafo, or at very least as a mains transformer of its own.
So search for the cheapest possible transformer that will fit the pinout, and you're probably fine.
Jakob E.
If it was custom-made, it would be MUCH cheaper to make it either as another winding on primatry trafo, or at very least as a mains transformer of its own.
So search for the cheapest possible transformer that will fit the pinout, and you're probably fine.
Jakob E.
I am hesitating to do so because I am not so active in the forum and I dont want to be seen as a stranger that is bombarding the forum whenever he has a problem...scott2000 said:
gyraf said:
Thank you for your reply Gyraf
Yesterday I was experimenting with using "backwards" step down trafos , as step up trafos.
I used 2 different trafos models 1.5VA 230V-12V, and I have fed 12V and 15V on the secondary.
To my suprise the 12V gave 160V on the primary, the 15V gave 190V and when pushing the secondary to near 20V, I got 235V. ( with no load)
With the same trafos when used in a normal way, feeding them 230V, I am getting 18V on the output with no load and 12,5V with load, so I expect that they are working right.
So i have concluded that trafos dont have the same behavior when used "backwards"
Could it be that because of the low VA rating, the transformer behaves this way, well I dont know...
I need to study more about transformers in order to tackle this...
Gyraf I would like to ask you a question:
How much tight in tolerance should the transformer output be ? Will it work right with 230V or 270V ?
From checking the schematics the 250VAC that are outputted from the transformer , turn to into 300VDC in order to power the tubes. With 280VDC or 320VDC is it going to work right?
Michael Tibes
Well-known member
+1 with gyraf here
I believe that you can use any transformer which gets you in the ballpark of around 220 V AC under load - it will be more with no load, so don't let that confuse you (how much more depends on the specific transformer). There are 2 22R resistors (technically one 11R / 2W) in series with the primary, my guess is that the voltage was over 300V so they added these to bring it down. The trafo says it was 15V to 250, that would be roughly 350 V after the rectifier and smoothing cap. The input voltage is probably 16V, not 15V, so it might have been even more. So they burn some energy here before the transformer in order to bring the voltage down. You could adjust these resistors (use a different value) if the voltage was a bit off with a different transformer. I do also believe that maybe +/- 20V difference on the 300V line would not make a big difference, if it was audible at all - as long as the the caps can handle the voltage? In case you try that you need to make sure that the voltage also does not exceed the cap rating when the tubes are not yet heated up, the voltage will be higher then for some seconds until current flows through the tubes. So I'd look for a 230 to 15 V 2VA transformer that fits mechanically as good as possible and see where this leads to. If you find one that fits mechanically and has a higher VA rating I'd go for that one.
Once you get this to work you might want to check if there is more current flowing than expected, if so then something else is broken as well which probably overloaded the transformer. I'd also check if anything else gets unusually hot to see if there are any other faults or design flaws ;-)
As mentioned before the technically best solution might be to have a custom mains transformer built which includes the 250V, but that seems a bit overkill and would most likely not improve the sound.
Hope this helps,
Michael
I believe that you can use any transformer which gets you in the ballpark of around 220 V AC under load - it will be more with no load, so don't let that confuse you (how much more depends on the specific transformer). There are 2 22R resistors (technically one 11R / 2W) in series with the primary, my guess is that the voltage was over 300V so they added these to bring it down. The trafo says it was 15V to 250, that would be roughly 350 V after the rectifier and smoothing cap. The input voltage is probably 16V, not 15V, so it might have been even more. So they burn some energy here before the transformer in order to bring the voltage down. You could adjust these resistors (use a different value) if the voltage was a bit off with a different transformer. I do also believe that maybe +/- 20V difference on the 300V line would not make a big difference, if it was audible at all - as long as the the caps can handle the voltage? In case you try that you need to make sure that the voltage also does not exceed the cap rating when the tubes are not yet heated up, the voltage will be higher then for some seconds until current flows through the tubes. So I'd look for a 230 to 15 V 2VA transformer that fits mechanically as good as possible and see where this leads to. If you find one that fits mechanically and has a higher VA rating I'd go for that one.
Once you get this to work you might want to check if there is more current flowing than expected, if so then something else is broken as well which probably overloaded the transformer. I'd also check if anything else gets unusually hot to see if there are any other faults or design flaws ;-)
As mentioned before the technically best solution might be to have a custom mains transformer built which includes the 250V, but that seems a bit overkill and would most likely not improve the sound.
Hope this helps,
Michael
Hi Michael,
thank you for your help, I deeply appreciate it, everything makes more sense now
I am going to buy a standard 3VA 230V-15V step down trafo and use it backwards as a step up, I am curious about the results.
I have also ordered a custom trafo which will supposedly output 260V (off-load), I will update the thread as soon as I have them in my hands.
A BIG thanks to all of you
thank you for your help, I deeply appreciate it, everything makes more sense now
I am going to buy a standard 3VA 230V-15V step down trafo and use it backwards as a step up, I am curious about the results.
I have also ordered a custom trafo which will supposedly output 260V (off-load), I will update the thread as soon as I have them in my hands.
A BIG thanks to all of you
Quick update:
I bought a generic 3VA 230V-15V trafo, and I tried to use it "backwards"
I fed 16V on the secondary, and I got 190 V on the primary.
Theoretically I should get near 240 V, I have no idea why this is happening. This also happened to the other trafos that I have tested previously...
With such a low voltage , I did not bother installing it.
Anyways ,
I am still waiting for the custom trafo that I have ordered, I will update the thread as soon as I have it in my hands.
I bought a generic 3VA 230V-15V trafo, and I tried to use it "backwards"
I fed 16V on the secondary, and I got 190 V on the primary.
Theoretically I should get near 240 V, I have no idea why this is happening. This also happened to the other trafos that I have tested previously...
With such a low voltage , I did not bother installing it.
Anyways ,
I am still waiting for the custom trafo that I have ordered, I will update the thread as soon as I have it in my hands.
scott2000
Well-known member
yekuku said:
Have any model numbers??? Are they single secondaries ???
HI scott, it is a simple 3VA 230V-15V trafo, just a single secondary.
Model number is Thai Lin TL 38s-150-213 (213mA@15V)
here is the manufacturer link :
http://www.thailin.com.hk/?page_id=1645
As it looks like , using an ordinary trafo in opposite configuration is not possible.
Anyways , I am still waiting for the custom trafo .....
Model number is Thai Lin TL 38s-150-213 (213mA@15V)
here is the manufacturer link :
http://www.thailin.com.hk/?page_id=1645
As it looks like , using an ordinary trafo in opposite configuration is not possible.
Anyways , I am still waiting for the custom trafo .....
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