Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Paramount => Topic started by: Rob Capizzi on September 01, 2021, 05:45:00 PM
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The board with 4 red LED's only one LED is lit and amp is not working. Tube glow, no output. I tried swapping cables and tubes from the working 1 and I narrowed it down to the amp itself. I inherited this setup from a family member. I am new to this lifestyle. But I have built guitar amps before. Thanks for anyhelp.
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Some Pics
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This is a Paramount, not a Foreplay.
Do you have access to a meter to measure voltages? They are listed in the manual, and measuring them and letting us know what they are will help us recommend what might need to be done to get your amp up and running.
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I do have meters. Where do I test, and what voltages am I lookng for?
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You'd want to look in the build manual. The terminal numbers are identified in the manual as are the expected voltages and how to measure them.
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Cool thanks, im going to online search for the manual unless you can conveniently provide a link. Appreciated. Also, I'm guessing the center block is a preamp?
I'm using 6ohm speakers with this setup. Is that OK?
The pot Infront of 300b is bias? I have some learning to do. Thaks for any help! Excited to hear these.
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Yes, the center component is the Foreplay III preamp; surrounded by the two Paramount power amps. (Incidentally, that's the same setup I have.) Manuals in PDF form are available for purchase if you can't locate the original ones - older ones were on CD-ROM, newer ones are downloaded. The output transformers can be wired for 4, 8, or 16 ohms but triodes are not very fussy, 6 ohm speakers will work well with either the 4 ohms or 8 ohm wiring. The pot is a hum balance control.
Bottlehead amps are often modified; if you post pictures of the insides, it may be possible to identify the more popular ones.
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Cool thanks, I'm picking up the manuals today. What do the four red LED's indicate? Also the one amp that works isn't as loud as I would think. I can max the foreplay vol knob and it's still very audible. Is it meant for low volumes?
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The LEDs are not used as indicators - they are "band gap" voltage references used in the current sources for the driver and its shunt regulator. If some of them are not glowing, it means the driver stage is not working correctly. The measured DC voltages, when you have them, will help diagnose the cause.
The amps put out 8 watts at maximum, and in my system at least, the Foreplay has much more than enough gain to drive the amp to clipping. Since I don't know the sensitivity of the speakers you are using, the output voltage of your source, or what exactly "as loud as you would think" means, I can't say much more yet.
One of the more common mods to a Foreplay is to reduce its gain, in cases of hair-trigger volume controls. It seems to me that might be a place to start - can you post a picture of the interior of the Foreplay?
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Foreplay
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Paramount guts
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Neat and clean work!
Both the amp and preamp appear to be unmodified stock builds. As a first check, you can see if the Foreplay tubes glow (including the gas regulator in the middle), and the two LEDs underneath (one on each tube socket) are lit.
The Paramounts are version 1.0, without the so-called "soft-start" driver mod.
Next step is the voltage checks.
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When I did some troubleshooting before posting here. the right channel works so what I did was swap all the cables on the side that I know is working to the left side. that did not work. I even swapped the tubes that were working, and the left side still didn't work. so I'm assuming it's not the foreplay but the left Paramount with issues. On the foreplay I am getting in-and-out left and right signals but no signal from the left Paramount. I will be doing voltage testing in the next day or so day or so once I feel comfortable enough to turn it back on.
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That's great that you are able to get the manuals!
Of most importance would be the DC voltages at all four pins on the 4 pin socket, as well as the DC voltages on the metal tabs of the two biggest transistors on the green C4S board.
Just those 6 voltages would tell us a whole lot about what's going on!
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Awesome
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Hi, still waiting on the manual. The 12at7eh on the non working para, is 130â°f opposed to the 190â°f on the working one. When testing voltages, I'm assuming test to ground? Thanks
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The only Tube that isn't lit is the 12at7 on the non working para,
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Wow, ok, I was getting votages, when I touched the meter probes to these two spots in the picture, it came on. Instantly.
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That kind of behavior would indicate a loose or broken wire.
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Super nice build. Something to pass down to your kids.
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Yes, it's staying in the family for sure.
Ok after the amp came on, I played music for about an hour. Sounds great, turned off,, went out for a few hours, wouldn't come on when I got back home. I once again touched the two meter leads, one on ground, one on pc2 transformer red wire tab that goes to the first tab on the board w 4 red LED's. It came to life,, Nothing seems to be loose.
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Something is loose in the amp. If you touch things and it magically comes on, you're moving the loose connection.
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I agree, just turned the system on, both amps working without probing. I'm going to meticulously check solders then voltages once I get manuals. Thank you
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Played for about 3 hrs, amp stopped, touched probes ground to tab on Pc2, the tab across from 6. Amp Came back on. Nothing loose.
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If you touch something in the amp with your meter probes and it magically comes to life, there's a loose connection or a broken wire.
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It definitely feels like magic! I still agree. Maybe a bad solder somewhere? I'm going to check around some more today.
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if you touch a terminal and it comes to life, you need to heat that joint and apply just a little more solder.
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What a wonderful gift, looks like there were plans to move the controls to the front of the pre base.
As for your volume question earlier, SF speakers (photo) aren't generally very sensitive (mid to high 80's) so 8W/ch probably won't rock the house.
Karl
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Karl, Indeed a great gift! I love em already. Good eye on the control plan. Good info on sf speakers thanks. Paul, Found a loose connection as you said, switch ground, thank you.
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Ah, spoke too soon. Back to the soldering board.
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It works for like a 1/2 hour and then stops so I go underneath and all I did this time was touch my needle nose to that bottom tab across from number 6 on PC2. The red wire that runs to the board with the 4 LED's when it's not working only one LED is lit when I touched my needle nose to it all 4 LED's came on and it started working.
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I'm still waiting on the manual so I could take proper voltage tests.
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Just a thought:
It seems likely that red wire is not reliably connected at both ends. Sometimes a wire is nicked when stripping the insulation from an end, and it eventually breaks inside the insulation. So check both ends of the wire.
If it's the one that goes to pin 1 of the tube socket, the end in the PC board may have a cold solder joint - that goes to the collector of a power transistor, which acts as a heat sink and requires extra heat and/or time to make a solid connection. So check the transistor connection as well as the red wire.
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Hi Paul, its the red wire that starts on the terminal Across from terminal 6 on PC2 tf, it goes to the 5 tab Distribution brown board Which then splits to 2 reds, 1 red going to the i on the AB greenboard the other red going to the yellow capacitor board. Hope that's clear. I'll look into your suggestion. It's been working for 3.5 hrs so far. Thank you
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Hi Paul, its the red wire that starts on the terminal Across from terminal 6 on PC2 tf, it goes to the 5 tab Distribution brown board Which then splits to 2 reds, 1 red going to the i on the AB greenboard the other red going to the yellow capacitor board. Hope that's clear. I'll look into your suggestion. It's been working for 3.5 hrs so far. Thank you
Took me a while, but I think I understand. (PC-2 is a plate choke; the terminal across from 6 is 5, the capacitor board is actually the power supply board). The wire connects the plate choke to the high-voltage power supply, so if it's not making good contact the output stage is not powered. The junction of the high-voltage power (under the green board) has several wires and is hard to see, so that's a likely spot for a marginal solder connection to happen.
These are just ideas for tinkering until the manual shows up; the real diagnosis starts when we have measurements, tinkering will then be much more likely to help!
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https://youtu.be/-hmWCrbHgdc
I just took this video now I turned the amp on once I got home only only one red light was on this time instead of touching number 5 on PC2I touched the tab on the Brown 5 terminal distribution.
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I'm going to clean this up and resolder some points
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Clean it and got same results
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Did you resolder the terminal you touched in your video?
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That is how a broken wire behaves.
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Yes soldered what I touched. Still looking for broke. Wires. Speaking of broken....300b socket. Maybe terminal is grounding out. Ceramic is broken see pic.
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You can very gently pull the tube out of that socket, then let super glue drip into all those cracks to keep it in place.
You could remove all the wires from that socket and take the socket out and it wouldn't cause the problem you showed on your video.
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I will do glue. I think I have an extra socket. There were spare parts. So can i turn amp on without the 300? Is there anything I absolutely should not do? I wouldnt want to damage further.
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Yes, you can run the amp without the 300B, but there isn't any reason to do that. I'm just saying not to worry too much about the socket, as I believe you have a broken wire.
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Cool thanks. Still can't find break. Here's another short vid. A little different result than last vid. Most likely picking up manuals today. https://youtu.be/O833ToxxOrc
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Sure looks like a broken wire.
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Received manuals today. Any info on the original pricing of foreplay 3 and paramounts? Thanks for any info
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The pricing moved around a bit over the years. You can use the internet archive to view our pages over the years: https://archive.org// (https://archive.org//) The products in question were both available around 2005 and stayed in the product lineup for quite some time.
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So cool! Thanks
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While amp is funtioning
Pc2
4 - 456vdc jumper to 6
5 - 468vdc
6 - 456vdc
10 - 444 vdc
Fc1
1- 66
2 -67
4 -67
5- 67
6 -72
7 -72
9 -72
10 - 72
Ot1
1-0vdc
2- 0vdc
3- 0vdc
5-69vdc
6-69vdc
300b
67 vdc
72 vdc
455 vdc
0 vdc
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There's no issue with any of those voltages.
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Thank you.. Yes. The amp is working. When it pops off, as soon as I touch any hi voltage metal for reading it'll come on.
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The transistor casings are even getting 400 plus volts. Is that normal?
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These transistors
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You have the manual right? It lists the voltages.
I've labeled a few on one of your pictures. If you have about 400V on both metal tabs of both transistors, I would question whether the 9 pin tube is lighting up on the top side.
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Yes I do have the manual and yes I am getting the volts that you Labeled on the photo. When I turned on the amp only the top left LED was illuminated (not working) as soon as I put my meter on tab 5 of PC2 to get a voltage reading it turned on (working). Read 477 vdc. Tapped 5 again, amp stopped working. Same voltage reading. Tapped again. Working.
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.
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also getting a faint Morse code static interference on the speaker output.
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When the amp is not working and one LED lit I am not getting the 225 V on the transistor on the greenboard
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But as soon as I tap the round transistor it comes to life
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If tapping things changes voltage dramatically, you should go through and reflow all of the solder joints in the amp and look for broken wires. If you'd like to send these in for repair, I do handle legacy repairs and I can get this amp fixed up for you.
-PB
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Cool thanks, gonna reflow first.
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223 vdc on the green board Transistor
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250vdc on one Transistor
500 on the other.
Little green board w 4 leds,the Transistor has 223vdc
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Still getting same issue. I'll check voltages again. Tomorrow with the manual.
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Voltages.
It's been on for over an hour. If it does fault, as soon as I goto take voltages, it comes on.
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If you look at the white printing Q2 on the A side of that PC board, then look at the large blue resistor next to it, you can see a typical solder joint that hasn't flowed out all the way. You can see the brown flux built up in the middle of the joint around the lead of the resistor, and that kind of joint can cause intermittent issues that seem to resolve themselves as soon as you touch them.
Having said that, it's also really important not to resolder any of the LED solder joints, as that can damage the LEDs since they have been sitting around absorbing moisture over the last decade or so, and heating them up will boil that moisture right out and blow the LED.
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Thank you! I do see that. Just reflowed.
It was playing a few hours today before it went out. When I took it to the bench, even when I went to test voltage on the main board Transistor, it came on. Hope that reflow did it. Cheers!
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Turned it on today nothing out of one block. When I unplugged it and looked underneath one LED was lit for quite a while after it was unplugged then it went out slowly put it on the bench, came on right away and then was intermittent. I will attach a video. https://youtu.be/n2ojGXXEJZI
Tested all 20 terminal strips. Voltage is properVariation 10 to 15%
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I'm also getting 123 to a 124 V out of the wall I don't know if that makes a difference but I when I tested the terminal strips I was using my variac at 1:19 like it says in the manual.
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If poking the power supply board is having those effects, there may be a loose part or a bad solder joint on the power supply board (which is a total PITA to remove).
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Really pretty much poking anywhere on here brings it back to life but yeah it does look like a pain in the ass to remove
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A broken wire would create these kids of issues. If you just barely touch the bad wire with your meter, it should easily set that off.
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If I barely touch ANYWHERE it will set it off. 1st board, 2nd board, transistors, tabs,.....anything high voltage. Meter touches, brings it back to life.
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If I had that amp on my bench, I would poke around to see what was most sensitive or what I could do to make the problem permanent, then take measurements to see what's missing.
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When I poke around with a wooden paintbrush on everything nothing changes as soon as I use any piece of metal whether it's needle nose or a screwdriver that's when it comes back to life
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I reflowed the 2n2907 . one LED's does not light anymore but I'm not getting the speaker ticking like I was before using the probe. Audio but no treble
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1. 445dc
5. 64dc
6. 64dc
7. 200dc
9. 270dc
11. 200dc
12 128dc
14. 57dc
15 1.2dc
16. 465dc
19. 275
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One LED out, no treble, 290vdc to b1 on 9 pin socket. Should be 195ish. Other 8 pins read fine. Touched terminal 11 all leds lit and treble came back, touched another terminal went dark again.
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You have a loose or broken wire. I wouldn't bother reflowing a transistor on the C4S board when you can poke the power supply board and cause things to drop out.
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Needle nose twist on that transistor brings to life. I reflowed a few times. . It's on. Nervous to touch anything. I've been staring at this for hours can't find loose wires.
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Poking on power supply board does not drop it out anymore I'm sending a video of me slightly twisting the transistor on the shunt board. I totally hear you and I agree on the wire. I just cannot find one and I've reflowed a lot on here and I'm feeling it's the transistor. https://youtu.be/Y3v7Z-IcCmQ
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I could assure you that it's only doing that when I twist that transistor not the board I could flip that board around and move it and tweak it and nothing happens. only when I twist that transistor
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Listening to music now. it will drop out after a few minutes but then come right back without touching anything.
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Is replacing the Transistor a bad idea? I'm kinda leaning toward that. It seems like that's where the problem is stemming from. When the amp is good I'm seriously tugging on all the wired connections and I can't replicate it unless I turn that transistor or does it by itself
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Go for it, you may find a broken wire when you remove that PC board ;)
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I get it. I wish i could find said broken wire. C4s. That board has been up for a while. She's been holding steady for an hour plus so far. Reflowing n2n907 seems to been showing the best results. That transistor seems to have the most sensitivity.
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Is it possible you have a damaged trace? Check for a crack in the vicinity of that transistor, right were it forms the eyelets ...John
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Kinda seems like it. She's holding pretty steady as of now since reflow.
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I can't see if any cracks by trace. Too small. I replaced the Transistor 2n2907a, it plays longer, cuts out a few seconds then comes back on for a while, the twisting of Transistor isn't cutting in and out like previous video. So I'd say it's a little better, but not fixed. I can't get it to cut out manually. I moved every wire and can't replicate it. It will cut out by its self, when I touch certain metal parts, with a metallic probe,like the Transistor I can hear static clicking in speakers like some sort of discharge. I go to sleep thinking what it could be. When it cuts out the d2 led on the b side remains lit.
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Barely Touched (A) side 2n2907a transistor collector w meter probe, amp turned off. Meters other probe was not connected to anything so it could have been a bic pen, anything metallic.
Therefore since the 2n2907a transistors Collector goes to the MJE5731A transistor's emitter, that is also sensitive.
When the amp cut out I touched the metal probe to 16 Randomly and it came back on. A wooden stick does not do anything. has to be metallic touching it. Tapped 5731a emitter, amp cut out, Touched 5731 base, came on. Those points seem to be the only point that makes a slight tick in speaker. The 2 transistors on A side. Also the center most csd01060 rectifier will Emmitt ticking thru speaker when metallic probe touches. It will also bring amp back on. Touching the mje350 w probe also cut off amp. Probing 907a base will turn it on.
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The 12at7 wouldn't have anything to do with this issue would it? because half of it operates as an actively loaded hybrid shunt regulator. I dont know, just asking.
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You have two amps and each has a 12AT7, so you can simply swap the tubes between amps to check for that.
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Doing that now. Just thought I'd ask to see if that's absolutely out of the question. Also the power choke tabs are sensitive too.
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Not the tube. 20 mins on, turned off, used ballpoint pen poked section A and came on. I have no clue. Sad.
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Part of the problem with what I'm seeing here is that when you poke at some connections with a meter and you get a noise, that may not mean anything is actually wrong with the amp. If you poke at one of the high voltage rectifier diode tabs with a meter probe and get noise out of the amp, that's not abnormal. The same goes for the choke connections.
We used to sell the soft-start retrofit for the Paramount that would provide a fresh set of parts and the updated driver board, but that has been discontinued.
One thing you could do is to switch the C4S boards between amps to see if the problem follows a board or sticks around in one amp chassis despite swapping C4S boards.
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Swapped the c4s. Issue followed.
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Is there any type of replacement?
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Two of these would give you the boards and a bunch of the parts you'd need:
https://bottlehead.com/product/stereomour-ii-shunt-regulator-upgrade-kit/ (https://bottlehead.com/product/stereomour-ii-shunt-regulator-upgrade-kit/)
If the bosses give the OK, we can send you the soft-start manual so you can source the rest of the bits.
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Hi, ok I've replaced both 2n2907a and 2 LEDs on B side. Playing strong fingers crossed. New leds are like twice as bright. A more pro solder station, magnify light, and 63/37 solder definitely improved my work.
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The B side LEDs should be a bit brighter since they have a bit more current going through them.
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Cool to know. Thanks. I would love to understand more about this circuit. Seems interesting.