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Old 15th May 2006, 06:56 AM   #501
AndrewT is offline AndrewT  Scotland
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Hi Key,
sorry my question now seems ambiguous.
Not, what grades does the manufacturer claim thay make.

What grades are available retail?

This information may help you decide what to buy.
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Old 15th May 2006, 07:40 AM   #502
quasi is offline quasi  Australia
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The gain of the 2sc2240 is not causing the problem you are experiencing.

More ideas;

Try checking the resistor values in the input stage (measure them). Also measure the values in the feedback loop (red, brown & orange can often be mistaken or poorly printed)

Check / replace the feedback capacitors (100uF).

Use the schematic that shows the current flows for each stage and verify (by measuring voltages) that you have these.

You can increase the gain of the amp using a 47k resistor.


Good luck
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Old 15th May 2006, 05:34 PM   #503
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Quote:
Originally posted by AndrewT
Hi Key,
sorry my question now seems ambiguous.
Not, what grades does the manufacturer claim thay make.

What grades are available retail?

This information may help you decide what to buy.
Hi Andrew,

The grades I purchased were the 2SC2240BL and 2SC1845F. Those were the only grades they carried, so those were all I could purchase. Both measured hFE in their respective ranges as I recall. If you need me to take some out and measure their hFE let me know.

Based on quasi's last message maybe the hFE DC gain is not really the cause of problem Miodrag is experiencing. I certainly do not have the knowledge to know if hFE is or is not the issue affecting both of Miodrag's modules.


Regards,

John L. Males
Willowdale, Ontario
Canada
15 May 2006 13:39
15 May 2006 13:44 Opps bad typo corrected
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P.S. My appologies in advance for any typo errors. If you cannot "decode" the typo or feel there is a typo (some typos are correctly typed spelling, but can be mix of wrong/omitted words) speak up and ask me to clarify. jlm
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Old 15th May 2006, 07:28 PM   #504
pejinm is offline pejinm  Serbia
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Hi guys,

Problem solved!
The store where I purchase my electronic parts gave me wrong resistor value(33k=3k3). I realy don't know how I did not notice this before.

Anyway now I'm really satisfied with the power of modules.

Thanks for help!!!

Soon I will post pictures of amp in the case...

Regards,
Miodrag Pejin
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Old 15th May 2006, 09:18 PM   #505
pejinm is offline pejinm  Serbia
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...Also I changed the 200ohm trimpot.It was old and wear out being from junked electornics. I could not set the bias current because of it.
Now everything is OK!

Again, thanks very much for help Quasi, John and AndrewT...

Regards,
Miodrag Pejin
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Old 15th May 2006, 10:48 PM   #506
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Miodrag,

Very happy you found the source of problem with quasi's help and are now a very happy audio person with the completed modules.

I was tempted to suggest check the resistors and capacitors. I just assumed not a likely case. You are very careful and thoughtful in what you do and why. Oh well we all slip up at times. I know from the places I buy parts the part in box is too often not what box is labled as. Sadly this almost certainly caused by the curtomers taking something out and forgetting where took from and just drop in what is most convient for them. I take meters for resistors and capacitors with me to be certain what I think I am buying for a value is the value I wanted.

I been burned by this misplaced parts problem a few too many times from places other than say an ElectroSonic we have locally here. ElectroSonic on their own initiative places transistors, bridges, diodes and ICs in antistatic bags on a part number by part number basis. The places I source from usually, as ElectronSonic does not have many parts/quanities allowed I need, are surplus places. Therefore the reason for caution using meters.

At least this resistor mix up did not cause a module to blow up for you due to store mix up. Which resistor was it that was wrong, R3 or R17 or both?


Regards,

John L. Males
Willowdale, Ontario
Canada
15 May 2006 18:53
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P.S. My appologies in advance for any typo errors. If you cannot "decode" the typo or feel there is a typo (some typos are correctly typed spelling, but can be mix of wrong/omitted words) speak up and ask me to clarify. jlm
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Old 15th May 2006, 11:25 PM   #507
quasi is offline quasi  Australia
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Aaaah..... the old resistor switcheroo.

Well done Miodrag. Enjoy your amp.

Cheers
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Old 17th May 2006, 05:49 AM   #508
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Default Hey good looking

What happens when the output of this amp is shorted?

I think I read the entire thread and I'm suprised more people are not trying this design and posting pics and feedback? I saw a +/-supply voltage versus number of output devices used table. I can't see it any more, repost?

Has anyone built this with a different PCB lauout?
I like it, it's on my list and I just ordered 20 IRFP's. If I get it up and running I'll have 3 power amps without cases but I'm working on it.

Shawn.
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Old 17th May 2006, 06:37 AM   #509
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Shawn,

I am curious where you are buying your parts from, locally or you mail ordered?


Regards,

John L. Males
Willowdale, Ontario
Canada
17 May 2006 02:43
__________________
P.S. My appologies in advance for any typo errors. If you cannot "decode" the typo or feel there is a typo (some typos are correctly typed spelling, but can be mix of wrong/omitted words) speak up and ask me to clarify. jlm
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Old 17th May 2006, 07:24 AM   #510
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Quote:
Originally posted by keypunch
Shawn,

I am curious where you are buying your parts from, locally or you mail ordered?
Like my ting says, I'm downtown TO and I like to buy local when ever I can. Local means visiting Active Surplus on Queen Street. Supremetronic on College Street now called Honson. Sayal Electronics in Scarborough and in Mississauga. More surplus at A1 Electronics. Still, you can drive to Hamilton for tube stuff from TheTubeStore.com (phone in orders in advance) I order direct from Hammond and Plitron and pick up my orders myself. Hammond has a museum to visit and they always give me a Tim Hortons coffee coupon

NOS tubes from an old TV repair guy in his 80's downtown and on the verge of selling his biz, basement used to be full of valves as the old fart loved them and couldn't part by tossing them in the garbage, the nineties hit and he's made a small fortune. Supply is running thin now and I'm certain he'll sell the building and collect his realestate millions. I went to one tube swap but it was all RF radio dudes and there was almost nothing going on regarding audio.

And of course mail order from everywhere. Duty is included when you buy from a stocking Canadian company like Solen in Quebec vs. Madisound in the U.S. The only thing I ever purchased from eBay was a laptop battery for IBM380Z and the supplier turned out to be in Ontario! Go figure?


And finally my own stash which I've been working on since I was a kid in the seventies

Happy hunting,

Shawn.
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