Modded TCM1150 APEX460 disaster

  • Thread starter Thread starter amzavareei
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There's been some good advice so far. The heater voltage (6VDC) needs to be verified AT THE TUBE SOCKET. If the heater voltage is present then the tube is definitely bad if it is not lighting up.

Next, I would check for the supply voltage of 106VDC as close to the tube as possible. If not present, then fix that.

Once you get past that, what really needs to be done is look at signals using an oscilloscope. If you don't have one, then I recommend that you print out the schematic of the mic and trace every connection to verify that nothing is missing.

I'm in the Los Angeles area. If you are somewhere close, you could bring it over and I would fix it for a nominal fee.

Phil and Marik: I removed the cathode follower circuit on all my mics and I think they sound better without it. It's easy. Remove all parts that connect to the CF circuit. Remove the heater voltage to that half of the tube. Wire plate, grid, and cathode to ground. Attach the capacitor that feeds the transformer to the plate of the first tube stage.
 
Which one is the heater? I'll try that tonight. I could just pop the tube in my preamp to test it too. I'm in NYC though, so I don't think I can just pop in. Thanks though! I know a guy that can fix it, I'd just rather not lug it around. Those capsules are so fragile. So I'm just gonna try and fix it at home, with all you people's help!
 
amzavareei said:
Which one is the heater? I'll try that tonight. I could just pop the tube in my preamp to test it too. I'm in NYC though, so I don't think I can just pop in. Thanks though! I know a guy that can fix it, I'd just rather not lug it around. Those capsules are so fragile. So I'm just gonna try and fix it at home, with all you people's help!
Click to expand...

Hey if you have/get any more info on the Avatars, could you post it as you get it? Thanks!
Also-- hope he doesn't run into any copyright problems with the Speaker people, but given that he's working in Avatar studios he might not.
 
amzavareei said:
Which one is the heater? I'll try that tonight. I could just pop the tube in my preamp to test it too. I'm in NYC though, so I don't think I can just pop in. Thanks though! I know a guy that can fix it, I'd just rather not lug it around. Those capsules are so fragile. So I'm just gonna try and fix it at home, with all you people's help!
Click to expand...

The shared connection for the heaters is pin 9 which goes to ground. The positive side of the heaters are pins 4 and 5. So you should see the 6VDC between each of those pins and pin 9.

The 106VDC should be between pins 6 and 9.

These are pins on the tube socket, not on the connector for the cable.

Hope that helps.
 
PhilGood said:
Yeah. I've been wanting to do that, but can never seem to find the thread. Gus had also posted some instructions on doing it, but I wasn't really able to follow his instructions. A before and after schematic would help it make sense.
Click to expand...

It was in Apex 460 capacitor change thread. Since I don't have to ask myself permision to quote it ;) , here it is again:

To make the circuit looking more like C24 is quite easy:
Remove R8
Cut traces from tube pins 6,7,8 and short them together
Connect C8 to juncion of pin 1 and R2
For the transformer use a high quality 1:8-1:10 Lundahl or Cinemag (depending on your taste).

For upgrading, besides aforementioned C8:

Ceramic C4 replace with polystirene cap of the same value with at least 150V rating.
You also can experiment with removing local NFB C6 cap, or replacing it with Black Gate cap of the same value.

You could as well get rid of C9-C10.

amzavareei said:
Which one is the heater?
Click to expand...

Re-read my message again. The heater is between tied pins 4-5 and 9.
 
OK. Since I've got 2 of these, I'm doing the CF removal tonight!

If I like it, then the other gets it! :D :D
 
O.K.
Crap
So now there's something wrong with the PSU
Only replaced 2 caps and 2 diodes
It was fine before
I was getting voltages on the pins a couple days ago
I don't remember a 6v
Remember a couple 106vs though
could something that happened in the mic with me fiddling around have fried the PSU?
Like if I fix the PSU, will my mic just fry it again?
 
Do you see any bulged or burst capacitors? Did you smell anything?

I wonder if there isn't a short somewhere.
 
I have found that the capacitors on the power supply are fine and don't need to be replaced, so it's best to leave them alone.

Which voltage is gone on the power supply?
Which capacitors did you change in the power supply?

If the 106VDC is gone, measure across each diode to see if the voltage is there. Verify you installed the diodes correctly. If it's not there, and you replaced one of the caps in that part of the circuit, you probably installed it wrong or it died.

If the heater voltage is gone, then you probably blew out the voltage regulator. The Apex 460 pdf has the correct schematic for the mic but the wrong power supply schematic. You need to use the power supply from the 450, it's titled "smapex450.pdf".
 
amzavareei said:
am getting like 175mv on pin 1 of the xlr
Click to expand...
If that's referenced to ground, then the problem is either the diodes or capacitors. Verify the direction in which the diodes were installed. Lift a lead of one of the diodes. Is the voltage still gone? If it's gone, then you probably installed a capacitor wrong, and probably fried it. If in doubt you can always put the old one back. They will work fine.
 
I opened the PSU, checked the voltage out the diode, 110V
checked it in the socket, 106V
plugged the mic to it, and the voltage is reading 102 on pins 5 and 6 to 9
nothing on 4 to 9
This might be the culprit

Hmmm... this doesn't jive with the schematic...

5 and 6 aren't supposed to be tied together and going to xlr2! 4 and 5 are...
and 4 is going to where 6 is supposed to be going, between R1 and R4

I am so sure I did not do that

someone broke in at night and did that to it

It must have come from the factory that way

it worked before!

who did this?

should I change this?

I swear I didn't do it!
 
And I am getting 6.7V between xlr 2 and 4, so that voltage is solid.
I'm really so sure I didn't do that to the socket pins
guess I should move them, huh?
 
It was like that when I got here!

The dog ate my homework. ;)

I sympathize with you. I've screwed up modding effects pedals and I'm not smart enough to figure out what happened.
 
Yeah, yeah, yeah. I've heard all those excuses when somebody's brought in a piece of gear for me to fix, that they had "worked on" themselves. (Just giving you a bad time).
Sounds like you found your problem. Good luck.
 
guess what.
I was counting the pins backward.
let me try this again!
 
So I'm back to where I was at the beginning of this thread. But now I know pins 4 and 5 are getting 6.7 volts, and pin 6 is getting 110, but only to chassis ground, not to pin 9.
weird...
 
There's your problem. You're getting current to the hot leads of the filament and plate, so when you check it to chassis ground you get a reading. Your lead from pin 9 is not making it to ground. Trace it.
 
If the CF is removed, what ratio transformer should be used?

Craig
 
craigmorris74 said:
If the CF is removed, what ratio transformer should be used?

Craig
Click to expand...

10:1, i.e. the stock one would work ;) .
 
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