-
Posts
760 -
Joined
-
Last visited
Content Type
Profiles
Forums
Events
Posts posted by sorenb
-
-
24 minutes ago, audiostar said:
Anyone by chance has 4x DN2540N8-G for me?
Mouser showing mid of September for these.PM me your address, I have plenty
- 1
-
Sounds like it's not only the +500V having a problem ...
Have you measured the drop across the "current setting" resistors for the various 10m90's?
Summing up those per rail, might shed some light on the matter ... -
The PSU's I have at hand consumes ~25W unloaded
Exploding 10m90's indicate massive current draw ... have you checked for any carbonization in the vicinity of those?
-
@jokerman777
Based on your post's I'd recommend disassembling both angle brackets, making sure all holes are properly deburred, and all the tappings are clean, also clean all semi's. Make sure the screws can go into the tapped holes using only finger force - if not re-tap the hole.
Re-assemble, using regular compound (the white stuff).
As for the buzz, you stated to have observed a flash in the region of the negative rails, and showed a burn'ed screw from the positive rail, showing that something was cookin here as well, and might have cause excessive current draw from the transformer causing it to buzz- 1
-
@jokerman777
The thermal compound looks kind of grey'ish ... do you use some exotic compound?
The screw needs to be able to slide into the 7721 without any force, otherwise it is too big.Maybe you found the cause of the HV transformer buzzing with "no load" ...
-
59 minutes ago, jokerman777 said:
Oh I got parts referencing a BOM where it says stth1512D that is obsolete and I used STTH15S12D instead, I suppose not going to make a difference?
STTH512FP is ready available and fully insulated.
If you look through the KGSShv thread, some had troubles with un-insulated rectifier tabs shorting.
-
@jokerman777looks like you did not use stth512's ?
-
18 minutes ago, simmconn said:
Good to know that the R ch works okay now.
As I understand, the channel has been working all along, just thrown off by the bal servo.
Wonder what the benefit of troubleshooting with the LF353 installed are? -
1 hour ago, audiostar said:
... I think @sorenb did a special power version of it.
Look at the Uberamp output stage.
- 1
-
.... are D19/D20 the correct value and both oriented correctly (not flipped)?
There are some good advice to be found in the posts from @simmconn, make sure you have read those.
-
1 hour ago, demonkuro said:
R+ always drifts between -0.5V and +0.5V. All EL34 are bright and hot, and I shuffle their order every time I test, but the result is the same.
Did you test Q24 (J79 in R+ ) ?
-
2 hours ago, demonkuro said:
It seems that only R+ is always working fine?
To me it seems R+ is not working correctly as it seems to be stucked at ~0V
...does it swing toward B+ at power off? have you tried pull the LF353? does the EL34 heater glow? maybe swap the EL34's in that channel?
-
5 hours ago, demonkuro said:
... The output R- to GND was -91V, R+ to GND was 0.05V, L+/L- to GND was -28.6V, ...
Provided the readings are right, I'd look at the right channel LF353 and re-check all the diodes in the right channel servo are properly oriented
if everything seems right, pull the right channel LF353 and see what readings you get. -
Kevin, wish you a UM66T08
- 1
-
11 minutes ago, Pars said:
OK, finally getting around to testing the GRHVs I'm building for the Carbon. Using Soren's post on pre-testing, I had some variances.
I marked up the schematic from James above.
- For the first test, using ~17Vdc thru an ammeter, I'm getting 0.5mA (not 2mA) (points A1-B1)
- For the second test, I'm getting ~1.3-1.4mA (points A2-B2), which matches Soren's figures.
- For the third test, I'm getting 10.5-10.9mA (points A3-B3). This may be referring to a Megatron HV900 PSU in Soren's notes below, and I'm not sure I'm looking at the correct points anyhow.
I have a 100K resistor paralleling the two 390Ks. Bringing the positive supply up on a variac until it regulates, it seems to be regulating at 55Vdc, which is about what I calculated. Boards are 1.8 version, single fat sw variants. The voltage appeared to be stable; raising the variac a bit didn't change the output.
Just checking because the first CCS test was considerably lower than what Soren saw. I did unsolder one end of the 100K resistor and rechecked, but no change.
Any thoughts, or just go for full voltage?
"you should get ~2mA" probably a typo, ~1mA is what I usually get, depending on the DN2540 ...0.5mA might be just fine
-
8 minutes ago, simmconn said:
The SiC did survive and still tested good all the way to 1700V on a curve tracer. I guess the ST9360 had a slow death and the BC557s gave up before more current could damage the SiC.
I've seen similar.
DN2540 leaking usually shows up as the output voltage of the PSU drifting.
As far as I remember the supplies breaking down was all wired as negative rails.
However, I have not seen it on any GRHV using the cpc1117. -
2 hours ago, simmconn said:
I’ve been using the DN2540 in TO-92 package since my first Carbon build without any problems on the amp board. However I’ve seen two instances where the DN2540 on the GRHV developed a Drain-to-gate leakage. That caused excess current thru the HV PNP. In one case (my own build) it was caught in time and didn’t do any real damage, in the other case (someone else’s board with a TO220 DN2540) the PCB was cooked, the ST9360 failed and brought down both the BC557s. The leakage problem is regardless of the DN2540 package. I’m suspecting in the cascode CCS there may be a corner case where it is stressed beyond the safe limit.
did the SiC survive (someone else’s board with a TO220 DN2540)?
-
Kerry most likely points to the zeners dynamic impedance which varies with current
1.3mA might operate the zeners too close to the knee
- 1
-
3 hours ago, dingding123 said:
Hi sorenb, thanks for the suggestion. I dont think the CCS was faulty, but I replaced the 10m90s with a new one from Mouser anyway. No change in bias voltage
The main GRHV voltages are normal: +396V and -406V.
Does the 806k and15k resistors have anything to do with setting the bias voltage?
did you check the zener string is actually seeing ground? and the 3k is actually 3k value, and sees source and gate?
- 1
-
4 hours ago, dingding123 said:
I understand that the bias voltage circuit is essentially a CCS into a zener string.
did you test whether the css is actually working?
-
On 6/2/2020 at 12:11 AM, powertoold said:
Hi all,
I have a KGSSHV (not carbon) 500V that has developed some low-level static / distortion with certain resonant frequencies on the left channel. I'm fairly certain it's caused by the KGSSHV since the static is reduced when I adjust the offset voltage to be more positive (currently at 40V offset; I believe ideal is 0V offset and 0V balance).
Would anyone have any insight into what is causing this static / distortion, especially since it is reduced when I make the offset voltage more positive?
Thanks!
@mwl168 is right 40V offset doesn't sound right.
The static may origin from leaking resistors or bad solder joints.
Check the 175k's (r10+r11) , r14+r29 and r7+r30 , as well as their joints -
5 hours ago, hyperma said:
Assembling another kgsshv carbon, this time the positive 400V keep droping from first second, don't know why.
Any diode or mosfet leaking? Don't know how to simulate
Check the current source at the front end
should source more than ~1.3mA or so -
On 3/23/2020 at 5:24 PM, blessingx said:
+ some human = Hopper
- 2
-
54 minutes ago, Hirsch2k said:
So I have finished the PSU and I am getting the expected voltages on all rails except Bias, which reads +380V to ground. But I guess this is expected behavior for Bias voltage without the proper ballast?
most likely you are measuring at BIAS output, having an output impedance of 5Meg ... and the DMM most likely 10Meg, so the +380V is actually 570V
Use the test point (TP) rather to get the right voltage
The ultimate DIY? A Stax SRM-T2!
in Do It Yourself
Posted
maybe start by checkin PSU rails at the AMP boards entry points, and check that all diodes are properly lit