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Old 4th October 2011, 03:48 PM   #1381
cersepn is offline cersepn  United States
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Quote:
Originally Posted by Tea-Bag View Post
I measure voltage across the 2Sk's then run a test signal (can be a line source) into the input, and measure AC out voltage from the output. The voltage should be in the 9-10v range.
Thank you, Tea-Bag. I shall try that out soon.

I forgot to mention, while i was testing the dcb1 i accidentally plugged out the right channel input while the CDP was still playing and there was a pretty nasty boom. Speakers still working, though i wonder if that killed the 2SKs/any other parts, which brings me to my next stupid question - is it always unsafe to unplug the rca in/out of the dcb1 while the amp and source is on?
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Old 4th October 2011, 11:15 PM   #1382
AndrewT is offline AndrewT  Scotland
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RCA (phono) type connections have a basic fault.
The hot contacts first on insertion and disconnects last on extraction.

This is recipe for disaster with "ON/Live" equipment.

Most decent connectors make the ground first and Return next with Signal last. But even these should not normally be connected or disconnected "Live".
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Old 5th October 2011, 02:40 PM   #1383
syklab is offline syklab  Hong Kong
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Hi Tea-Bag,
Will there be any problem with in-rush if I use 4x 6800uF instead of the original 4x 4700uF ?
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Old 5th October 2011, 03:02 PM   #1384
Tea-Bag is offline Tea-Bag  United States
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Quote:
Originally Posted by syklab View Post
Hi Tea-Bag,
Will there be any problem with in-rush if I use 4x 6800uF instead of the original 4x 4700uF ?
Not that I have experienced.
I have one that's 4x10,000uf for phono supply and no issues with fuses or components failures.
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Old 5th October 2011, 03:13 PM   #1385
AndrewT is offline AndrewT  Scotland
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My second power amp had 4 off 4700uF as smoothing.
I changed to 12 off 6800uF for smoothing. That did not result in a fuse blowing problem.
The start up current of the 250VA transformer did cause a problem.
When mk3 came along the 625VA transformer needed a soft start, but the 80mF of smoothing still did not cause nuisance blowing.

There are two different problems. Start up current of the transformer and charging current of the smoothing.
The peaks of these two different short term loads do not coincide.
The soft start for the transformer is hardly needed after a few cycles of AC have passed through the primary winding.
While the transformer is "starting up" it cannot supply significant power/current to the smoothing. That peak charging current reaches it's maximum "after" the transformer has reaching operating condition.
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Old 5th October 2011, 03:55 PM   #1386
cersepn is offline cersepn  United States
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Quote:
Originally Posted by Tea-Bag View Post
I measure voltage across the 2Sk's then run a test signal (can be a line source) into the input, and measure AC out voltage from the output. The voltage should be in the 9-10v range.
Hmm, I tried this test and all 4 2SKs measure well in that range.

Quote:
Originally Posted by Salas View Post
Some discharge when you were handling the boards maybe, can't say. You need to feed signal and follow it, to see where it stops. If you don't have an oscope, DVM on ACV can detect. Feed 300Hz (test CD, or there are software generators free, google up) at about 1VRMS and see until where it makes it by probing the path, starting from input RCA, finishing at output RCA including interconnect cables. With DVM on Ohm you can check continuity, if relay engages, etc. 100% audio circuit jfet matching helps offset naturally.
Salas, would you care to elaborate more specifically on what i'm supposed to doing? Using DVM with ACV of setting 200, I fed 300Hz, probed the live and ground, input gave me 3, volume pot as well, but no readings on the dcb1 outputs ... ?

I tried googling more on how ACV works but still confused on what it really does.

While feeding the test signal, i also tried measuring DC (set to 200 mv). There were values at the input and output.

Any further help is greatly appreciated!
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Old 5th October 2011, 04:47 PM   #1387
Salas is offline Salas  Greece
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Set it at 20V range. Do you trace up to the 1V AC (or 3?) that you feed it as you turn up the DCB1's volume pot, going to the pot, exiting it, on the input 220R, on the Jfets, on the output 220R, on the relay, on the relay output, does it stop reading somewhere? Where exactly? That should be the problem connection or part.
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Old 7th October 2011, 01:25 AM   #1388
cersepn is offline cersepn  United States
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Originally Posted by Salas View Post
Set it at 20V range. Do you trace up to the 1V AC (or 3?) that you feed it as you turn up the DCB1's volume pot, going to the pot, exiting it, on the input 220R, on the Jfets, on the output 220R, on the relay, on the relay output, does it stop reading somewhere? Where exactly? That should be the problem connection or part.
Hmm, there is AC from pot, exiting pot, but nothing on the two input and output 220Rs. Nothing on jfets if i measure AC, but there is 9.50+ DC on them. Not sure which pins of the relay i should be probing... i checked the datasheet but i don't see where they mentioned that bit of info
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Old 7th October 2011, 01:32 AM   #1389
Salas is offline Salas  Greece
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That result fixes attention to the route portion from board signal input pins to input 220R. Do you use connectors to the board? Check there is connection continuity. You should be probing for signal the pins connected to the 220R resistors. There should also be -9.5VDC or about there to the other side.
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Old 7th October 2011, 02:58 AM   #1390
cersepn is offline cersepn  United States
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Pcb Connections are soldered directly. Okay, in a nutshell, I'm supposed to see dc on the relays, all 220r resistors, output and 2sk. And ac on the RCA inputs?
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