[
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2008, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]
76.22.120.252
In Reply to: RE: Seduction C4S voltage readings posted by nicetom@netscape.com on May 12, 2008 at 14:36:45
Lots of questions in this and the previous post (above), so I'll try to answer some but it may be confusing!
>> Here are a few voltage readings from my troubled Seduction C4S board. Referring to #13 in the manual, which puts a colored circle beside each of the MJE 350 (rectangular black) transistors, I measured to the center pin (which connects to the wire to a Seduction terminal). Results: Black 139 VDC, Yellow 74.4 VDC, Blue 63.3 VDC, Red 77.8 VDC.
As CB said more tersely, this shows that three of the four current sources are providing the right current to the tubes - that is, all but the one with the black circle. From the middle pin of the MJE340 the wire goes to T42 then through the 220 ohm carbon resistor to pin 1 of the tube socket. If the resistor is damaged, or if any of the solder joints are bad, there will be no current and the current source will lock up at the supply voltage of about 140 volts.
Later you said "Nothing looked wrong with the wire between 42 and the black circle transistor." Looking is not an adequate substitute for measuring - measure the voltage or resistance all along that path to determine whether the circuit is properly connected.
>> I also measured each end of the four 237 ohms resistors, getting 141 VDC in each of the 8 measurements, and the two 75K ohms resistors, getting 138 VDC at the inside ends and 0 VDC at the ends closest to the end of the C4S board.
These are more or less correct values, indicating that the 237 ohm resisors are connected to the power supply, one end of the 75Ks is connected to the powered circuit, and the other ends are connected to ground.
>> I also tried to measure the wire going into a hole at the end of the C4S board, and got a scary snap and spark, but no damage done as far as I can tell, to multitester or C4S board.
I assume you mean one of the wires described in instruction number 11 or 12? These wires go to ground and to the power supply high voltage respectively; a slip of the test probe will short the power supply and make a big spark. Happens all the time.
>> Nothing looked wrong with the wire between 42 and the black circle transistor.
See above.
>> While looking, I noticed that 44 is now idle--a wire into it but nothing out. Or should I just say only one wire to it, never mind in or out? Not so with 34, which has that very hot wire going to the C4S board.
No problem. You removed the 18K load resistor from there in step 7; that function is now served by the C4S board through the wire to T42.
>> (Can anyone explain that scary snap and spark?)
See above.
>> I measured resistors to tube sockets, with one deviant result, with 'ohms' understood: A1 231, A2 238, A6 230, B1 297, B2 225, B6 230. All color-coded the same, for 221 ohms. Is that B1 divergence bad?
These are carbon composition resistors, not very precise. That value is acceptable, though it is slightly out of spec for the part. (What? You didn't measure the 220 ohm resistors from tube pins 7 ?!) :^)
>> Can anyone tell me where the inner C4S LED's should get juice from?
They get their juice through the adjacent 75K resistor. High voltage comes in on the wire from T34 and goes to the non-banded end of the right-hand LEDs (as shown on the manual). The banded end connects to the non-banded one of the leftmost LED, and the banded end of that LED goes to the 75K resistor which goes to ground.
Follow Ups:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2008, Audio Asylum, all rights reserved ]