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TO-3 SYMASYM

@Curryman

You asked: Will they also run from 2x18V AC?

Michael Bittner's SYMASYM was designed and tested using 25 VAC transformers. He recommends DC values in the range of +/- 35 V and +/- 40 V.

Please refer to this thread, if you want to know more about the SYMASYM:

http://www.diyaudio.com/forums/soli...ifier-designed-michael-bittner-our-mikeb.html

Maybe 18 VAC will work. You have to change several things, though, and it may end up being a bad sounding amplifer.

So: my short answer is: NO.

Best regards - Rudi_Ratlos
 
Dear TO-3 SYMASYM friends,

tonight I did the 1st power-on on my 2nd channel of my TO-3 - SYMASYM-PCB.

Since my eyes do no more have the capabilities of a hawk, I took my 7 MB digital camera, made a picture of the solder-side of my PCB
and verified that I did a good job.



http://www.abload.de/img/joe0142lcl.jpg

This looks quite good!

Then I went downstairs, connected the PCB to my PSU, installed 10 Ohm resistors across the empty fuse-holders, shortened the RCA input, ... and ... powered on.

No smoke?!!

Well: this is what I expected.

Then I turned the trim-potentiometer for the TEMPCO / BIAS - adjustment counter-clockwise, and turned, and turned, ..., nothing happened,
..., and turned and turned - then, all of a sudden: the DMM reads: 1 mV dropping across both TO-3 emitter resistors, 2 mV, 3 mV, ...
the 10 Ohm resistors are about getting very hot, ... - it works!!! :cheers:



http://www.abload.de/img/joe022gaep.jpg

I have documented the procedure how to adjust the quiescent current in my "TO-3 SYMASYM Builder's Manual".

Be sure: this is a very, very outstanding AMP.

Best regards - Rudi_Ratlos
 
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Monitor the voltage across the Vbe multiplier, as well as Vre.

You will see the Vbe varying instantly in response to turning VR.
Then as Vbe approaches the output bias voltage required you can expect to see Vre starting to take off.

4 soldered in loops, for tapping in test instruments, makes a big difference when developing a new amp.

Why do you still use the remote server to hold our pics?
 
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This is an update of the current order:



http://www.abload.de/img/image1sppm.jpg

I will close this group-buy as soon as I have received Rudi_SW's order.

I sent Rudi_SW a parcel with quite a number of PCBs, TO-3 transistors, emitter-resistors, ..., some time ago, but his parcel got lost.
I filed a request for investigation then, but DHL cannot tell me, where his parcel has gone.
I am now struggling with DHL to refund the parcel's worth.

I advice everybody to spend some extra € and ask for insured shipment.

Due to the fact that I do no more have to pay the tooling costs and due to the quantity of PCBs ordered ,
I will be able to offer you the PCBs for a lower price than given above.

This is the current status of my own build:



http://www.abload.de/img/joe0013pmo.jpg

Remember: these are the Version I - PCBs.
The Version II - PCBs (the ones that are offered in this group-buy) have the drivers mounted on the ALU-L profile!

Best regards - Rudi_Ratlos
 
I promised you some details on the "Soft-Power-On" circuit.
Here they are:

The schematics:



http://www.abload.de/img/spo_schematicsk8xt.png

The PCB (size: 80 x 65mm; I will increase the distance between the mains' tracks and the mounting holes!):



http://www.abload.de/img/spo_topview_smallk8x5.png

The function:

Those of you, who are going to build the TO-3 SYMASYM and will equip it with one or two transformers rated at > 500 (!) Watts totally,
may also want to have a "Soft-Power-On" circuit that prevents the fuses from being blown due to the high inrush current that flows,
when you apply voltage to your big transformers.

Connect the "hot" wire of your 115VAC resp. 220 VAC mains voltage to Pin 4 of connector X1 and the return wire of the mains to Pin 4
of connector X2 on the right side of the PCB.
Connect the primary leads of your transformers to pins 1-3 of connector X1 resp. to pins 1-3 of connector X2.

The hot wire is connected to an on-off switch as well.
This switch can be a very small one, being capable to switch 220V/150 mA.
This is the switch to turn your AMP on.

The onboard-transformer is a EI30 type, 12 VAC/1.5 W.

Its output is rectified and regulated by a 7812 voltage regulator.

As soon as the 7812 shows 12 VDC at its output, relay K1 (Omron G6D-1A-12V) switches on, and the current is flowing through 2 thermistors
with a total resistance of 44 Ohms, thus delimiting the inrush current to the transformers to about 5A.
(In case you are operating from a 115VAC mains voltage, take 2 thermistors of 10 Ohms each).

The 7812 voltage regulator also provides the voltage for a LM555 timer, that triggers its output on pin 3, as soon as the delay,
defined by R1/C1, has passed.
Then relay K2 will be switched on, bypassing the thermistors, and the current can flow without any limitation.

I used 100K/10µF as R1/C1, giving a delay time of about 1 sec.
This time is big enough for the transformers to get "settled", and you do no more be afraid that any fuse in your house will be blown.

This circuit has been prototyped (without transformer / rectifier - I use an existing 15VDC LAPTOP power-supply) and is in use.
The cost per PCB will be about 8€ (due to additional tooling costs).

Best regards - Rudi_Ratlos
 
T03 SYSMASYM v2 PCB dimensions?

post#1 of this thread states T03 SYSMASYM PCB dimensions are 150x100mm but to me this seems to apply to rev1 of the PCB.

The current version (rev2, with driver transitors on the alu L-profile) appear to be bigger but I couldn`t find any info about it (dimensions are also not stated in the Builder`s Manual, BTW: thanks again for it Rudi).
Please what are the precise dimensions of this PCB revision?