If I power up the filament transformer with no loads attached it blows the 2amp fuse... Weird, if I power it up with no loads and no soft start it trips 16amp rcd in workshop. Connected two 6c33 filaments and all is OK.. Inductors hey🤔
Toroids can be magnetized when shut off, depending on the position of the AC waveform. The next time you turn it on, the existing magnetic field causes the core to saturate and so there is a large inrush current. This can blow a fuse quite easily. When there is a load the random magnetic field is vastly reduced.
My ht transformer is 500watt, it has two identical 120v-0-120v windings, 250 Watts each. The ares audio pcb only has connections for one set. I have worked out the phase so I can parallel them up.
There are quite a few errors on the screen printing of the psu pcb, but if you follow the connection drawing and ignore the printing on the pcb, you will end up with less fuses in the bin than me.
There are quite a few errors on the screen printing of the psu pcb, but if you follow the connection drawing and ignore the printing on the pcb, you will end up with less fuses in the bin than me.
I have spent a bit of effort on understanding how the amp works. I was trained in BJTs ages ago and have not worked with electronics for literally ages - I am 55 now.
The link below takes you to an attempt at working out the DC points and also how the circuit works when amplifying - in particular the output. The input seems simple enough.
When working out the DC points, I got gate-cathode voltages for V2 and V3 that must be wrong at +13V.
If anyone is curious, follow the link.
https://docs.google.com/document/d/12sj_sfgz3dbpvQn0ets6HTI-GRXVPl9xP3fVC-9lXKg/edit?usp=sharing
The link below takes you to an attempt at working out the DC points and also how the circuit works when amplifying - in particular the output. The input seems simple enough.
When working out the DC points, I got gate-cathode voltages for V2 and V3 that must be wrong at +13V.
If anyone is curious, follow the link.
https://docs.google.com/document/d/12sj_sfgz3dbpvQn0ets6HTI-GRXVPl9xP3fVC-9lXKg/edit?usp=sharing
@CaptainChaos, I have never seen that drawing of the connections , the one you posted above with your markings on it. Looks like you got it from Ares, going by the font (!). Could you share it? I have a drawing with lots of coloured lines and the tubes drawn in. The more info, the better. I am in Oslo, by the way.
AH, I have a different soft start PCB from you. Ares has more than one version.
AH, I have a different soft start PCB from you. Ares has more than one version.
The heater cons for 6c33 (C) are marked wrong on silk screen ! This drawing is correct. and the 6volt on the left is all wrong way round eff is transformer in ect.. I have 4 X 6.3v outputs on my transformer and i had to connect all four to get all four supplies out of the board. The conections on the left do the EFF heaters and the ones on the right do the ECC or vica versa. one side connects to ground through resistors and the other to HT4 -150v
I have finely got One working channel on my Ares / Tim Mellow 6C33 OTL amp. It has taken some time to get this far. There are quite a few errors and conflicting information in the Ares information. So I thought I would outline what i have discovered.
The first PCB I assembled was the soft start / protection PCB. This went all ok, until I tried to install the relays. The pin spacing was wrong, I contacted Ares about this and they told me they were aware of this, and I needed to "bend the relay pins out a little" but the relays wouldn't sit properly on the board. So i drilled the holes larger and soldered them in all nice and flush, only to find I had created O/C tracks as the through-plating was gone from my drilling. wire jumpers fixed this, but it's not very pretty! I will sort this out at a later date, maybe Ares will correct this in later batch of boards.
Next build was the Power Supply. The only errors on there are on the silk screen printing. Where Filemants 'C' connect. I connected them the same as the rest and ended up with a 12 volt 9 Amp short for a millisecond, until it blew the leg off the screw terminal ! I have to take responsibility for this a little, as if i had studied the Ares diagram, instead of what was printed on the board, I would of avoided this. Replaced screw terminal and broke another...all good. there are other labaling errors on this PCB. Transformer 6v in and ECC filaments reversed See pic's
The Driver PCB Is all OK.
The Drawing for the wiring of the underside of the amp (new version) is completely wrong. I re-drew it and rebuilt it 3 or 4 times before i got it right. It wasn't until the last time that I realised, Ares had also the Cathodes and Grids reversed on there drawing. See my New working drawing.
Hope this will help, now to build other driver PCB, source 4 More 6C33's, and Build a nice chassis to put it in.
The first PCB I assembled was the soft start / protection PCB. This went all ok, until I tried to install the relays. The pin spacing was wrong, I contacted Ares about this and they told me they were aware of this, and I needed to "bend the relay pins out a little" but the relays wouldn't sit properly on the board. So i drilled the holes larger and soldered them in all nice and flush, only to find I had created O/C tracks as the through-plating was gone from my drilling. wire jumpers fixed this, but it's not very pretty! I will sort this out at a later date, maybe Ares will correct this in later batch of boards.
Next build was the Power Supply. The only errors on there are on the silk screen printing. Where Filemants 'C' connect. I connected them the same as the rest and ended up with a 12 volt 9 Amp short for a millisecond, until it blew the leg off the screw terminal ! I have to take responsibility for this a little, as if i had studied the Ares diagram, instead of what was printed on the board, I would of avoided this. Replaced screw terminal and broke another...all good. there are other labaling errors on this PCB. Transformer 6v in and ECC filaments reversed See pic's
The Driver PCB Is all OK.
The Drawing for the wiring of the underside of the amp (new version) is completely wrong. I re-drew it and rebuilt it 3 or 4 times before i got it right. It wasn't until the last time that I realised, Ares had also the Cathodes and Grids reversed on there drawing. See my New working drawing.
Hope this will help, now to build other driver PCB, source 4 More 6C33's, and Build a nice chassis to put it in.
Just wondering if anyone measured the distortion profile of the original Mellow OTL from low 0.1 watt to high power?
Look at this thread:
https://www.diyaudio.com/community/...m-mellow-6c33c-otl.257100/page-3#post-6820292
https://www.diyaudio.com/community/...m-mellow-6c33c-otl.257100/page-3#post-6820292
Hello everyone.
I started to build a Tim Mellow amplifier, now I have a question.
Why do the filaments of the 6j32p tubes not turn red?
p.s. the heaters are not interrupted and there is a voltage of 6.3v on pins 4 and 5
I started to build a Tim Mellow amplifier, now I have a question.
Why do the filaments of the 6j32p tubes not turn red?
p.s. the heaters are not interrupted and there is a voltage of 6.3v on pins 4 and 5
does it matter if the amp works just fine? try cleaning pins with fine 1000 grit sandpaper and use deoxit on the sockets...
Hi Tony,
Thanks for the reply .
Now I'm back with some updates.
This amplifier is not yet in operation, now they are at the level of preparing the tubes.
So I connected all the filaments to the transformers for a period of 72 hours (according to the recommendations on the forum) In this I noticed that the 6j32p tubes do not heat up as much as the others (I think they have a maximum of 35 degrees Celsius compared to the V1 tube which you can't keep your fingers on it.
Hi Koonw.
Believe it or not, I measured the resistance of the heater and it is 100 Ohm, then I fed the filament with the current source with 6.3 v, and nothing.
I started to increase the voltage up to 12 v...
The outcome? the filament looks perfect and does not seem to be overpowered. How do you explain this?
6j32/ef86'6267 tubes consumed very little power if at all, naturally they will run cooler than the 6c33 running at around 80 watts per bottle compared to those peanut tubes at around 2 watts...
Heater resistance (100 ohms) doesn't seem right. 6J32p are all produced in Russia after 2012, but 6.3V heater version I think it can not be a MULLARD NOS UF86 TUBE 12V VERSION EF86 6267 as it is produced before this date, unless 6j32p (12.6V ver?) has been produced elsewhere in Europe before Russian.
I just dug out some distortion measurements I made a while ago:
100mW: 0.09 %
1W: 0.18 %
5W: 0.20 %
10W: 0.18%
20W: 0.17%
This was at 1kHz, using a Keithley 2015 THD Multimeter.