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Old 12th May 2013, 05:01 PM   #701
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Default The first sweet taste of success

The first challenge today was to get the wrongly inserted 2n5551 right, I did not have any desoldering wick left.
So I had to revert to a desoldering pump and brute force, I did have two spare pairs of matched 2n5551 and used these.
Removed the jumpers, to activate the CAP-Multiplier

Second: Getting the L profile and the power transistors in place.
Rudi, thanks for the tip to use some shrink tubing, that is a live saver.
I did not use paper as insulator between L profile and PCB, I did have some extra TO-3 micas ( 8 ) and used these.

Third: Power on, no blown fuses, no smoking parts, all OK.

Forth: Set the bias current, R channel had the DMM on the wrong setting, so adjusted too high for a few seconds, turned all the way back, set the DMM the right position, and re-adjusted, set value to 29 mV.
L channel, made sure the DMM was set to the right position :-)) no problem setting to adjust to the same 29 mV. it creeps up slowly, and the power transistors get warm (not hot). R channel gets warmer then the L channel.

I did power down after about 10 minutes, (L profiles where warm, but I did not have a problem handling them with my bare hands).
I want to attach the heat sinks first before continuing, and make a temporary backplate for the input connectors and speaker terminals.

So I expect, that next weekend it will play some music.

Rudi, thanks for the PCB's it is a pleasure to make a system with them.
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Old 12th May 2013, 05:15 PM   #702
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Joe , How deseparate are you to get TO3 boards?Shall I sell mine to you?

Last edited by meanman1964; 12th May 2013 at 05:23 PM.
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Old 12th May 2013, 10:39 PM   #703
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If your not going to use what you have I,ll take them off your hands. joe
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Old 12th May 2013, 10:40 PM   #704
evette is offline evette  Canada
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Mr. Meanman what else you have? joe
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Old 12th May 2013, 10:57 PM   #705
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Joe ,send you a mail
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Old 19th May 2013, 07:57 PM   #706
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Default The sweet sound of success

Yesterday was a nicel day, I heard the sweet sound of success, the system is playing music, thanks to Rudi's high quality PCB's.

I have had JBL E20 and KEF LS-50 speakers connected to the system.

I could not hear tonal differences to a previously build symasym with MJL 3281A / 1302A transistors (boards not from here). That is good since I really like the sound these designs transfer.
I just re-read the start of this thread, and the reason for this specific design is to drive lower impedance speakers, that is not the case here, the system will go to a relative.

For me this build is a success and I praise all that helped to design the layout and improve the initial system.

For the keen eye I have added two more holes to each the L profiles for better contact to the heat sink.

The previous comments on the heat sink selection must be taken seriously. The heat sinks, SK 85/100 SA (100 mm high), get more then hand warm (not hot) when listening to music at moderate output level for more than an hour, the transistors stay relatively cool.

NOTE: For builders without proper tools, connecting the L-profiles to the heat sinks is a time consuming process.
Most important use new drill bits to drill the holes in the heat sinks, this saves time and nerves.

For me personally when there will be a rebuild of "Roender's FC-100" and I don't miss out on the GB I will join the party. (Wow, is just read Roender's FC-100 prototype and builder's thread, I will start reading that thread.

Grtz
Bert
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Old 20th May 2013, 03:18 AM   #707
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Default The missing picture

Somehow the picture got detached from my last message.
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Old 21st May 2013, 09:29 AM   #708
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Default Electrolityc cap values

Hi,

I was just going through the BOM (the Reichelt shopping cart Rudi provided as reference), and it struck me that there are electrolytics with a voltage rating of 50V and 63V, as well as from the Panasonic FR and FC series.

- What is the reason behind chosing different series?
- What is the reason behind chosing different voltage ratings (except C4 with 10V)

Would it be possible to take all caps from the FR series with a 50V rating (higher lifetime, lower impedance)?

Maybe someone can help me out here!

Regards,

Rudolf
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Old 21st May 2013, 09:35 AM   #709
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Rudolf, when I defined the cart of the BoM, some of the capacitors have not been on stock and I just put in the cart what has been available.
You can of course take all electrolyts, film caps, ..., of the same brand. 50VDC will do (supposed you will operate the SYMASYM from 25VAC transformers).

Best regards - Rudi_Ratlos
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Old 3rd June 2013, 06:36 AM   #710
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My SymAsym is nearing completion. Just waiting for the toroid and the multiplier cap transistors Can't wait to fire this up and start working on the case
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