EZ Tube Mixer Support Thread

[anjing]

Hi Ian,
    Good news, i can get 6 modules(5 channels+1master) to run by ajusting the limiting pot. Before i could only do 5(4+1) Now i just need to assemble more modules and test again.

Regards,

Pierre

 

[ruffrecords]

Holger is a genius!!
...

I wished that would be true.

I was a bit irritated that you've mentioned in a mail that you've spent 50 quid for a couple of 32 pin connectors.

Not quite a couple - it was for six to fill a backplane PCB but even so very expensive

The Harting BTW link points to a D-type connector.
I use the DIN 41612 32-pin C type for the project. The male-female combo should't be more than ~2.50€.

That's odd - I just tried it and it points to a Harting DIN  4162 32 pin C type at Farnell.

Cheers

Ian

 

[ruffrecords]

Hi Ian,
    Good news, i can get 6 modules(5 channels+1master) to run by ajusting the limiting pot. Before i could only do 5(4+1) Now i just need to assemble more modules and test again.

Regards,

Pierre

Excellent. Mine looks almost identical to yours. The lower pot, white on your picture, is green on my PCB. Otherwise they are the same.

Cheers

Ian

 

[ruffrecords]

Last night I tried the International Power 12V 5.1A supply, unmodified, driving six cards and it worked. There was quite a delay (more than 15 seconds I would guess) from turning on the supply until the tubes could be seen to glow but it did work. I need to check the output volts at power up to see if the foldback current limit is triggered.

Cheers

Ian

 

[anjing]

Hi Ian,

Thats how mine acted with 5 cards.

Regards,

Pierre

 

[ruffrecords]

Hi Ian,

Thats how mine acted with 5 cards.

Regards,

Pierre

I just did the test again but this time with a DVM across the 12V output. When you switch on the output goes to about 0.8V for a few seconds, then slowly creeps up to about 5V then shoots straight to 12V and the heaters can then be seen to glow. If you then turn off and on again  within a few seconds it goes straight to 12V. I tried leaving it a couple of three minutes and it still wnet straight to 12V. So I am now leaving it half an hour and I'll repeat the experiment.

Conclusion - it is definitely inrush current causing the supply to go into foldback current limit. The small current it does allow is enough to gradually warm up the heaters and it eventually exits foldback limiting.

Once I establish if 30 minutes is a long enough cooling period, I'll repeat the test with the current limit pot turned fully anti-clockwise.

Cheers

ian

 

[ruffrecords]

I have been thinking some more about heater supplies. It finally dawned on me that the LM338, LM317 and TL783 all have identical pin outs in their TO220 versions. Looking at the datasheets it is clear they also have near identical application schematics. So it occurred to me that a single PCB could be used for all of these regulators. Most of what is needed is already on my phantom power PCB, including provision for a modest heat sink. Calculations show this should be sufficient for a 12V heater regulator passing just over 1 amp; enough  to power a couple of Eurocards. For a sub-rack we need over 3 amps which the TO3 version of the LM338 can candle with a suitable heat sink. The spacing of the mountings for the small heat sink of the phantom board is less than the spacing between the fixings of a TO3. However, if you drill an extra hole you can fit either. The TO220 heat sink fixings just happen to be off centre so when you add the extra hole, the TO3 ends up pretty near centre of the PCB. The idea is that with this extra hole you can add a couple of pillars and mount a TO3 LM388 on a heat sink to the back of the PCB. There's a 2.3 degree C/W heat sink that is almost exactly the same size as the phantom PCB and calculations show this should be able to provide over 4 amps at 12V.

Bottom line is I think I could come up with a single PCB that could be used for 12V heater supplies at various currents or phantom power or even regulated HT using the TL783. Oh no! it's the Universal Regulator!

This could be generally useful so I think I will start a separate thread fro it in the drawing board.

Cheers

Ian

 

[ruffrecords]

I have done some further tests on inrush current. Using the International Power PSU as supplied I powered up with my DVM in series with the 12V supply set to the 10A range. The current starts at a fraction of an amp, gradually increases to about 3 amps, then jumps to over 6 amps at which point the tubes begin to glow. The current then reduces to a steady 2.8 amps.

I then repeated the test with the I.LIM pot turned fully anti-clockwise and it refused to power up. I realised I had previously traced the pot circuit from underside the PCB so when I decided fully anti-clockwise should defeat the foldback current limit it should have been clockwise. So I repeated the test with the pot fully clockwise. The current rapidly reaches about 6.8 amps then falls back to 2.8 amps as the tubes start to glow.

I conclude that setting the I.LIM pot fully clockwise does defeat the foldback current limit and that the regular current limit then operates.

Cheers

Ian

 

[anjing]

Hi Ian,
    I just finished assembling channel #6 . Seven eurocard's all power up nicely. So that's one problem taken care of!

Regards,

Pierre

 

[ruffrecords]

Hi Ian,
    I just finished assembling channel #6 . Seven eurocard's all power up nicely. So that's one problem taken care of!

Regards,

Pierre

Excellent. We live and learn.

Cheers

Ian

 

[Holger]

PSU, 90% finished. 10A heater, 12V SMPS for lamps and relays, Ian's HT PCB (need a 400 mA  transformer in the future) JLM AC/DC for 48V, +/- 24V for future purpose.

 

[ruffrecords]

@Holger,

Today at last I received a 12HP 3U Fischer module from Farnell. I tried fitting in a twin line amp card and it will not fit - the tubes are too tall. How did you get my PCB to fit into one of these??

VERY nice power supply build. I like the idea of the meters. What connector did you use for the outputs?

Cheers

Ian

 

[Holger]

I've played a bit with my proto rack and found that it would be possible to put the modules 12 HP apart. Ian's default width is 14 HP.

-pic removed-

The advantage is that ist would be possible to use standard enclosures like this for EQs:

-pic removed-

Sorry for bringing that up. My idea at that time was to mount the EZ cards just with a front panel and use the 12 HP cassettes for the EQs. In a standard 19" rack it would have been possible to fit seven 12 HP modules. But I found that even an EQ requires more front panel space for knobs etc. so I abandoned the idea of using 12 HP cassettes.
Later I received a 14 HP cassette which allowed me to fit the EZ card:

http://www.groupdiy.com/index.php?topic=48039.msg653093#msg653093

So the EZ amp card does not fit into a 12 HP cassette. I currently don't have a good ventilated Fischer cassette for the EZ cards.
For the EQs etc. I use 14HP cassettes from the Fischer 'HB' series.

The connector is a 10 pin Harting HAN system.

 

[ruffrecords]

I've played a bit with my proto rack and found that it would be possible to put the modules 12 HP apart. Ian's default width is 14 HP.

-pic removed-

The advantage is that ist would be possible to use standard enclosures like this for EQs:

-pic removed-

Sorry for bringing that up. My idea at that time was to mount the EZ cards just with a front panel and use the 12 HP cassettes for the EQs. In a standard 19" rack it would have been possible to fit seven 12 HP modules. But I found that even an EQ requires more front panel space for knobs etc. so I abandoned the idea of using 12 HP cassettes.
Later I received a 14 HP cassette which allowed me to fit the EZ card:

http://www.groupdiy.com/index.php?topic=48039.msg653093#msg653093

So the EZ amp card does not fit into a 12 HP cassette. I currently don't have a good ventilated Fischer cassette for the EZ cards.
For the EQs etc. I use 14HP cassettes from the Fischer 'HB' series.

The connector is a 10 pin Harting HAN system.

OK, understood. It is surprising how much front panel space is needed for EQ.

Where do you get the 14HP cassette from?

Cheers

Ian

 

[anjing]

I've played a bit with my proto rack and found that it would be possible to put the modules 12 HP apart. Ian's default width is 14 HP.

-pic removed-

The advantage is that ist would be possible to use standard enclosures like this for EQs:

-pic removed-

Sorry for bringing that up. My idea at that time was to mount the EZ cards just with a front panel and use the 12 HP cassettes for the EQs. In a standard 19" rack it would have been possible to fit seven 12 HP modules. But I found that even an EQ requires more front panel space for knobs etc. so I abandoned the idea of using 12 HP cassettes.
Later I received a 14 HP cassette which allowed me to fit the EZ card:

http://www.groupdiy.com/index.php?topic=48039.msg653093#msg653093

So the EZ amp card does not fit into a 12 HP cassette. I currently don't have a good ventilated Fischer cassette for the EZ cards.
For the EQs etc. I use 14HP cassettes from the Fischer 'HB' series.

The connector is a 10 pin Harting HAN system.

OK, understood. It is surprising how much front panel space is needed for EQ.

Where do you get the 14HP cassette from?

Cheers

Ian

I think the cassette pictured in the earlier thread was the schroff one. Wasn't there a problem with the offset of the backplane connector?

Regards,

Pierre

 

[anjing]

Hi everyone,
  Here is a revised fader faceplate design. I'd like a second opinion or some suggestions...I'm planning on using a toggle switch for the mute function.

Thanks!

Pierre

 

[ruffrecords]

@Pierre: Looks good to me. Is that an original RCA knob?  What pots and knobs are you using for the AUXes?

Cheers

Ian

 

[braeden]

Hi everyone,
  Here is a revised fader faceplate design. I'd like a second opinion or some suggestions...I'm planning on using a toggle switch for the mute function.

Thanks!

Pierre

I would suggest adding a circular scale around the Pan knob, it helps to guide the eyes. On first glance I kinda struggled to see what that knob was actually for.

When designing things I try to consider how easy it would be for someone else to find a particular feature/knob, which is great if you intend on selling the board at some point.

Otherwise, don't bother! :

Braeden

 

[anjing]

@Pierre: Looks good to me. Is that an original RCA knob?  What pots and knobs are you using for the AUXes?

Cheers

Ian

I did order some original knobs from leeds radio, but they are just a tad bit too small. The one on the picture is some replicas i found on ebay. I'm not sure i would recommend them to anyone but they will do for now.

For the aux's i am using the same pots as Holger. They are 1/8 shaft so will need to find some adaptor to use the knobs on the picture. The knobs are Davies 1900 clones. I will be using those same knobs for the gain pots of the eq. I like them they have a small footprint but i think they look good.

Regards,

Pierre

 

[ramshackles]

Ian, I saw you were using the expensive harting DIN connectors at about £9 each.
I don't know if you know that they do another for £3.50, part numbers:
receptacle: 2289392
connector: 109-6838
I bought the cheaper ones and it fits the eurocard just fine. Only difference as far as I can tell is that the current rating (for the connector at least) is 2A...I think the more expensive one is 6A? I don't know if this is problematic.

I've been looking for the module cassettes, but I can't find them on farnell - does anyone know if you can get the cassettes from farnell?

I've also lost the thread where Ian mentioned the PCB-front panel brackets. There was a cheaper one and an expensive one..I think this is the expensive one:
http://uk.farnell.com/schroff/60807-181/bracket-to-fix-pcb-to-panel/dp/2292872

But can't find the cheaper one?