Jump to content

i'm on a roll... the kgsshv


kevin gilmore
 Share

Recommended Posts

Welp, I promised a progress report, but so far there is no progress.

The first time I had originally ordered parts for the kgsshv, there was no BOM.

I went off of the board silk drawing. This time I used the latest BOM.

I found a mistake after receiving the parts for the repair this time around.

The part listed on the BOM as FQP8N80C should read FQPF8N80C.

So the regular TO220 with the exposed metal tab were shipped, they should be the all plastic jobbies.

Hello Mouser! (again)

Link to comment
Share on other sites

That thought crossed my mind but I dont have any extra oxide insulators and I wont use plastic screws.

Craig Sawyers had a good idea using extra long flanged insulator washers along with stainless screws

coupled with the oxide insulator "tombstones".

I bought those(oxide plates and long shoulder washers)the last time around

to re-do the small kludged (raised) heatsinks that KG didn't approve of.

I should have bought extras, but did not.

So I am going to reorder again and do it the right way.

It's not expensive, so I dont care.

Hey Doc, if yer reading this please update the BOM. Thanks!

Link to comment
Share on other sites

Craig Sawyers had a good idea using extra long flanged insulator washers

I can't claim that long bush idea was mine - Inu tracked those down as part of his T2 build. He used plastic screws as well, but the fact that the bush goes almost all the way through the alumina insulator means that steel fasteners work perfectly.

Only thing to watch is that although the outer diameter of the bush *should* fit in a TO220 hole, tolerance stack up sometimes means that it is a very tight interference fit. Feel the force, kgsshv buider, feel the force. Believe it will go in and it will.

Link to comment
Share on other sites

updated spreadsheet. if there are any other errors let me know.

fqpf8n80c... lots in stock at future electronics.

If you want to be fancy about it, on the small heatsinks, remove

the pins, use them upside down, thread the area on the other

side where the pins used to be, and then drill and tap a new

#4-40 hole for the transistor. Use ceramic insulator, bushing

and stainless screw.

Edited by kevin gilmore
Link to comment
Share on other sites

I can't claim that long bush idea was mine - Inu tracked those down as part of his T2 build. He used plastic screws as well, but the fact that the bush goes almost all the way through the alumina insulator means that steel fasteners work perfectly.

Only thing to watch is that although the outer diameter of the bush *should* fit in a TO220 hole, tolerance stack up sometimes means that it is a very tight interference fit. Feel the force, kgsshv buider, feel the force. Believe it will go in and it will.

They are going in alright, my dremel with a drill rasp saw to that.

The interference fit was a bit too tight, no problem chasing the TO-220 mounting holes

about ~.002" with a dremel. The extended length shoulder washers* plopped right in the last time around.

*Mouser p/n: 532-7721-3PPS

Gonna do it again this time, using the ceramic oxide tombstones as Nattonrice suggested.

Mouser does not carry the all plastic fqpf80n80c sand. (26 week lead time)

So I'll be using the TO-220 sand I have with the exposed metal mounting tab.

I've never used future electronics, Mouser is my friend. :P

Edited by livewire
Link to comment
Share on other sites

  • 2 weeks later...

Well this really sucks and blows.

It seems the Post Office has lost my Mouser repair parts order.

It had a tracking number, they say that they delivered it.

It sure wasnt delivered to my address unless there is someone

in the neighborhood stealing packages out of mailboxes.

Am gonna place another duplicate order, this time shipped using another carrier.

We'll see. Wait, wait, wait.

Just curious. There are at least four other people out there with kgsshv board sets.

It would be nice to hear of your progress in building this thing.

Seems that I am going nowhere fast, maybe someday I'll hear music from it.

Link to comment
Share on other sites

No I didnt call them. I guess I could, got nothing more to lose.

Mouser does have a disclaimer on their website trying to discourage

customers from using the USPS for their shipments due to this type of crap.

I wish that they would use "signature confirmation" instead of the "delivery confirmation" option.

With the former, they must deliver it to someone and have them sign.

With the latter method any mailman can misdeliver it and sign off on it.

(what I suspect happened here - my mailman is a demented old puke)

UPS or Fedex aint much better, if I'm not home they will leave the parcel on my doorstep

in plain view of any dirtbag walking by on the street, ripe for the pickin.

Link to comment
Share on other sites

  • 2 weeks later...

Got the repair parts in from Mouser, so troubleshooting the psu continues.

Things still aint right, the negative 450 volt rail is still outputting only 15 volts.

The positive rail which was completely dead, now has voltage, but it is off the charts.

(at least as far as my 600 volt limited Fluke DMM is concerned.)

This much higher than normal voltage is also backfeeding into the filter capacitors.

o_O! That's not good!

I am not able to read it, so I guess it is time to dust off my old Simpson 260

that is in storage in the garage, which is capable of reading up to 1000 volts.

The only (high) voltage that is still normal on the psu board is the 580 volt bias output.

At least I didnt blow that up. The 15 volt supply is also working again.

What would be nice would be knowing some nominal testpoint voltages so I could test for those.

I'm too stupid to figure out what the base/gate voltages should be that are fed in from the

rather complex (to me) sub-circuits. (such as the "battery" circuit)

Blub, blub, blub. (i'm trying to tread water here!)

Link to comment
Share on other sites

Yippee!

I got the +450VDC psu rail working again.

No more over-voltage issues to deal with.

Now with one side good, I can revert to comparitive live testing

between the good side and the bad side.

Hopefully, I'll get the negative rail back up soon.

That is if another parts order to Mouser isnt necessary. :rolleyes:

Link to comment
Share on other sites

(long version)

About a month ago while testing I slipped with the probe

and shorted the two pass regulators. (fqpf8n80c)

They were toasted along with the 10m90s and 2SC4686A sand

in the positive rail. The 24 volt zener popped too.

I had replaced them all yesterday and started to test again today.

After noting the bar graph on my Fluke shooting past 600 volts

and blanking the display, I shut it down.

I went back to cold comparitive testing using the resistance scale.

It was then noted that one of the devices that I had changed was

shorted. (the 10m90s) The new one on the negative rail had an in-circuit

reading of ~3K ohms between the gate and the other terminals,

the new one on the positive rail was ~28 ohms.

So, I guess it was a bad part or that the soldering did a number on it.

This time around I bought extra sand.

I replaced it a second time and everything is now working fine again on the +450VDC side. :)

Edited by livewire
Link to comment
Share on other sites

  • 2 weeks later...

In a word, yes.

I've replaced almost everything on the negative side

Cross checking against the good +450 volt side is difficult

due to the groundplane linking everything when hot.

If there were two separate identical 1/2 psu boards instead

that were linked like in the schematic, it would be more straightforward for

newbie comparison testing. It was working originally, so my goofs created

a hole that I must now crawl out of.

Knowing some testpoint voltages at the regulators

and battery for instance could shed some light on the trouble spot(s).

I wanna say "I'm done, stick a fork in me", but i'm not there yet.

Link to comment
Share on other sites

Is this the same board that got fried twice? I know you don't want to hear this but if it were me I'd repopulate on a new PCB since it was working before it got fried so that means there shouldn't be any errors in the PCB, pre-fry. And since the positive and negative rails are basically the same, other than deriving the bias from the positive rail, if you can't spot the problem on sight it may take a really long time.

If you don't want to go that route, maybe post up some pics?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...