Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Topic started by: kgwrocks on May 16, 2020, 01:05:08 PM
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Hi Paul,
Doc B. suggested that I ask you if I still had issues...
I replaced the power supply caps, etc per the earlier instructions on one of my amps. The original voltages were quite high. I hooked my octopus/oscilloscope up and found that one of the LT1431IZ shunt regulators was not working. So I ordered so new ones. I put in the replacement, but I can't get voltage on B6 to adjust to 215VDC.
Here are the measurements on my 2 amps:
#1 (unmodified):
B+1 (first cap) 447 VDC
B+2 (second cap) 432 VDC
after 15k0 5W resistor - 198 VCD
B6 - 215 VDC
# 2 (with PSU upgrade)
B+1 (first pair of caps) 451 VDC
B+2 (second pair of caps) 437 VDC
after 15k0 5W resistor - 234 VCD
B6 - 267 VDC
Any ideas? Can I provide any more info that would help?
Kevin
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Is this to me or to Paul Joppa?
Can you post up some photos of what you're up to?
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Yeah, pictures would be good.
You said you replaced the caps, etc - does "etc" mean the hefty cathode resistor which must have replaced the series 1.8K and 1.5K resistors that came with the Paraglow II upgrade package? No other changes from stock?
Just trying to be sure we understand the starting point. PB has done the necessary mod more than once, but I'm interested in this thread too, especially for historical reasons.
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I'm having trouble up;loading the pix, so I'll try breaking them up
This are the unmodified and modified amps
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more pix of the modified amp
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and more
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Here the original thread:
"The minimum process for rebuilding Paraglows involves mounting a pair of 6 lug terminal strips on each power transformer,
then moving the power supply to that location. We usually used at least a pair of 220uF/250V caps in series to get 500V
rated caps. The next area to address was to dramatically increase the wattage rating of the cathode bias resistor.
For the recent rebuilds I have done, I have used 25-50W parts instead of the 10-12W parts provided with the kit.
These run cooler and last much longer.
Along with the new cathode bias resistor, a new cathode bypass cap is also called for.
The series caps should also have 1 megohm resistors in parallel with each cap to equalize the charge across the caps.
This update is fairly tricky to implement because of the additional parts being sandwiched into the rather primitive
layout (I can say that since I did it) and it might be something that is best sent to PB to install."
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A few questions and photos of my amp attached (Note: mine has the Buddha CMC filter and RRSF and some parts upgrades - otherwise a regular PGII).
I just wanted to confirm what parts I need (doing both amps)
4: 6 lug terminal strips (https://www.mouser.com/ProductDetail/Keystone-Electronics/822?qs=sGAEpiMZZMvlX3nhDDO4AO8cnfwRjH5XUfPLeM1KNm8%3D)
8: 220uF/250V caps (https://www.mouser.com/ProductDetail/Nichicon/UVR2E221MRD?qs=sGAEpiMZZMtZ1n0r9vR22VJXtNfMoEIxa1JdRAAGvYw%3D)
8: 1M resistors (carbon film?, power rating?)
2: new cathode bias resistor - Currently using Arcol 3k3/25W - is that ok? - note this was the value measured from JT's original parts
2: new cathode bypass cap 220uF (https://www.mouser.com/ProductDetail/Nichicon/UCY2D221MHD?qs=sGAEpiMZZMtZ1n0r9vR22awqI6nzE%2FsTCBQlAGkaPmE%3D)
NOTE: the new amp does no have the RRSF
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OK, things are making more sense now. The balancing resistors can be a 1M/0.25W, that's sufficient.
Your new power supply is working properly. The Tucker shunt reg board is possibly not working, or you have half a driver tube not lighting up or half a driver tube that's not conducting anymore.
So, verify that both halves of the 9 pin tube are glowing, then swap 9 pin tubes between amps. If that doesn't fix the issue, then it's down to the Tucker board. When I run into those, I just put the Paramount soft-start driver into the amp and call it good.
As far as the Arcol 25W resistor goes, can you send a link to the part you bought?
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I'll add that, based on my recent work on pboser's Afterglow, the 3300 ohms is correct, but its bypass should have a higher volt rating - it has
250v 200v across it. (added: But the startup transient goes much higher.) There are 315v and 350v rated parts - in fact that's probably what was used for the HV cap replacement.
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Here is the part: https://www.mouser.com/ProductDetail/ARCOL-Ohmite/HS25-3K3-J?qs=sGAEpiMZZMtlubZbdhIBIEidPY%252Bx%2FLaaoOHGETo8UTQ%3D
I used the same set of tubes to test the 2 amps, so I don't think that is the issue.
I can hook up the octopus and scope up again and test the other parts on the Tucker boards.
I replaced the trim pot and the shunt reg on the 1 board (on the problem amp). Note, when I first built it, I had a similar issue and JT fixed it for me (before I had the scope/octopus). JT used a Huntron Tracker.
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Filaments are all good.
Comparing the parts one the 2 boards with the octopus/scope looks the same.
LEDs all come on. The 2 resistors in parallel near the trim pot look a little dark. I can't read the values.
When I try to adjust the trim pot, the voltage only changes a volt or so.
Do you recall the resistor values?
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My 3k3 resistor is 25W
250/3300=0.076 amps
250*0.076=18.9W
So that part should be fine
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Uh-oh! I think I made a mistake. With the PGP8.1 you get 200v across the cathode resistor and 60mA through the 2A3. I'll fix my post.
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What is the startup voltage? Note: I have a center tap ground lift switch installed. If I need a 50W part, I can get them. But I should maybe get some new ones to try. I seem to recall that they are 6N1P.
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My 3k3 resistor is 25W
250/3300=0.076 amps
250*0.076=18.9W
So that part should be fine
No, not by a long shot. The 25W rating on the Arcol HS-25 series resistor assumes you have it mounted to a piece of aluminum that is 83 square inches and 1/16" thick. If you had the whole top plate with no holes in it and no other sources of heat, that would only be 60 square inches. In reality the top plate isn't worth much as a heatsink for a resistor like this, as there are holes in it and other source of heat. These are rated for 9W with no heatsink, and the max temperature rating for the resistor is 200C, so it's entirely possible that 9W of dissipation gives you 200C. We work really hard not to run any resistors or transistors in our amps over 100C.
For 19W of dissipation, I would want a resistor or combination of resistors rated for 60W and not a type that requires a heatsink.
This is what I use in my Paraglow rebuilds:
https://www.mouser.com/ProductDetail/Ohmite/L50J3K0E?qs=sGAEpiMZZMtlubZbdhIBIMQod%252BtVNHwBcdGFIgmte38%3D (https://www.mouser.com/ProductDetail/Ohmite/L50J3K0E?qs=sGAEpiMZZMtlubZbdhIBIMQod%252BtVNHwBcdGFIgmte38%3D)
To trim it out to 3.3K, a ~300 ohm 5W resistor can be added in series. These are cumbersome to mount, but they are large enough not to experience a whole lot of temperature rise.
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Wow! Shows what I know. Thank you for explaining clearly.
Do you have a part number for the 300r0/5W resistor? Is there anything else I should replace (as long as I am ordering parts)?
Could this have something to do with my original issue?
My guess is that the resistor got too hot and took the shunt reg with it. I will check if the Arcol resistors died.
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This should work nicely for you:
https://www.mouser.com/ProductDetail/Vishay-Draloric/AC05000003000JAC00?qs=sGAEpiMZZMsPqMdJzcrNwnDHAJTsQNMje3pExDIkwVo%3D (https://www.mouser.com/ProductDetail/Vishay-Draloric/AC05000003000JAC00?qs=sGAEpiMZZMsPqMdJzcrNwnDHAJTsQNMje3pExDIkwVo%3D)
For what it is worth, I have worked on a bunch of Paraglows over the years, and I've never had one come in with both of those driver boards still functioning, that's why I end up just replacing them.
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Do you have info/parts for the soft start circuit? Sounds more convenient than my ground lift switches.
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You can get a good chunk of the parts you'd need from our Smash-up upgrade. Beyond what's in that kit, you'd need a few extra small parts to replace a few of the resistors in the kit, as well as a few extra parts if you want to implement the adjustable biasing feature that we added.
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JTs early shunt reg boards had a potential issue in that they would blow if the trimpot was turned all the way to the low end. Pretty sure that he would preset them close to where they needed to be when he packed those kits in order to avoid the issue.
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Thanks for all of the help. So I will order the "smash" kit. What else do I need (e.g., resistors)?
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Just took a quick look at the smash kit. Does this replace JT's boards? And is the kit for both monoblocks?
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Are you going to keep the 5965?
On the Smash-up schematic:
37R4 R1 becomes 90.9R
44K/4W becomes 330K/3W (Vishay PR-03)
49R9 R1 becomes 177R
100K R2 becomes 300K/3W (Vishay PR-03)
147K R4 becomes 330K/3W (Vishay PR-03)
0.1uF/400V Cc becomes 0.1uF/630V
Add one 33K 1/4W resistor to Y+/Y- on B side
Add one 10,000uF/6.3V cap to Y+/Y- on B side
Add one 300K/2W resistor between OB and -Reg
To add bias adjustments, you would populate a TL431, 4.99K resistor, and 10K trim pot on the unused regulator section of the Smash-up.
The new board wires in like the Tucker board, but you don't need that resistor between the power supply and the board, just connect it directly to the high voltage supply.
You'll have to work off the schematic of the Smash-up and the tube datasheets to get it wired in.
-PB
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My amps currently have 6N1Ps from JT's original upgrade.
Does the smash come with different tubes?
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Question on this: "The new board wires in like the Tucker board, but you don't need that resistor between the power supply and the board, just connect it directly to the high voltage supply."
is that the 15k0/5W that goes from B+2 to B6?
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You'd need to go back to 5965s. The Smash-up would come with a 6SN7 you don't need, but they do sometimes come in handy ;)
Yes, the 15/5W resistor goes away.
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are the values you gave me for the 5965?
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and what power rating on the other resistors?
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That is what I would use for 5665s. To be totally honest, this kind of work can be unforgiving of any mistakes, and is certainly something I could pop in for you if you sent these in for repairs.
Otherwise, there's no manual for this. If you asked nicely (and ultimately order the Smash-up upgrade to use for parts), Doc B. may be OK with me sending you the Paramount soft start retrofit manual. That would be about 90% of the instructions you would need, though it's for a slightly different amp with a 5670 and not a 5965.
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I ordered the smash.
What if I do all of the other upgrades and have you install the smash?
I doubt that Doc has mailed it to me yet.
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I mean, it won't really matter all that much to me one way or the other. For the cathode bias resistors in the standard Paraglow, I have a ton of 2K/25W tubular resistors, and I use one of those and another 1.2K 10W resistor in series with that.
I also somewhat frequently just rebuild these on 8x10 chassis plates. This gives me room for a really beefy 3K/50W tubular resistor that runs nice and cool.
In either case, I do enjoy refurbishing the old kits.
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Hi Paul,
I got the smash kit in the mail today. I guess I will order the new giant resistors and the resistors for the smash kit.
I think I will try to get the amps working without the smash kit. If I get stuck on the smash kit installation, could I get the amps to you to do that part?
cheers,
Kevin
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Sure thing!
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Hi Paul,
I'm going to order more parts soon. I am concerned about the power rating of the 3k0/50W in series with the 300r0/5W. Don't they both have to be 50W?
If now, does the order they go in matter? Which one should go to ground?
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Ohm's Law tells us that power is current squared time resistance. Current is 0.060A.
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Update. I have updated the PSU on both Paraglow IIs. I also replaced the big resistors on the 2A3 tubes. B6 is still around 260VDC instead of 215VDC.
So I guess I will send or deliver the amps to you to do the smash upgrade and get the amps dialed in. I found the 5965 tubes that came with the kits. So I'll get those to you as well.
Please let me know the arrangements.
thanks,
Kevin
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Did you try rolling in a fresh pair of driver tubes? I think those Tucker boards used the 6N1P right? Those aren't exactly the longest lived tube in the world, and when they get flat, that plate voltage will start drifting up.
Otherwise, you can just order the flat rate repair service for two amps, and that will take care of what you need done. It may take a little while for the boxes to go out and come back to me, so toss a note in one of the boxes that's just a print out of this thread and I'll remember what to do.
-PB