Uh oh. I screwed up my Apex 460

T

teekay

New member
Hi there, DIY guys!

I've been a reader of the forum for a while, but I've never posted anything... Now I think I might need your help.
I was wondering if anyone could give me a little bit of help on this Apex 460 that I modded so well that it doesn't work anymore. : /
I got my capsule / kit through Canadian Audio Distributors... so that's a transformer/capacitor/capsule mod.

I must have screwed something up on the way doing this, but i'm not sure what, and now I'm at a bit of a loss. Basically, it seems as though it powers up, and the tube glows orange, but no sound is actually produced. If i crank up the gain all the way, then I can hear some of my voice through the capsule, but it's a very small amount and it's incredibly noisy.

I'm not particularly savvy with electronics, so I'm wondering if anyone might be able to help suss out what the problem might be. I have a multimeter, but unfortunately no voltmeter or anything of the like.

I've also included a bunch of pictures in case that might help.

Please let me know your thoughts!

TK


OH! all the pictures are viewable at imgur.com/a/mDu2K . I tried posting them in this thread, but they were too big, apparently, and I couldn't create a link either (sorry about that).
 
A multimeter has a voltmeter function. You should start by measuring DC voltages everywhere and posting the results (preferably on a schematic so it's easier to read).
 
I hate sounding like an a$$hole (well, not really), but if you are an admitted 'non-savvy' electronics person, you should start learning with a much simpler project. The schematic is out there, and you're going to have to bully your way through it and figure out where the signal goes south. You can start with B+ voltages, and some resistance measurements can't hurt. Your B+ should be on pin #1 and pin #6 of the tube socket, there should be 6.3VAC filament voltage on pin #4/5 (wired together) and pin #9, and you might get 2.7K to ground at pin #3 and 270K to ground at pin #8. After that, a scope and some real troubleshooting chops are needed. The input is pin #2 and the output is pin #8. Good luck, and learn your lesson!
 
Nah, you don't sound like an asshole for saying it. To be honest, I've actually put together a bunch of electronics with kits, and I've fixed/modded other electronics, too.

I suppose I underestimated the shoddiness of the Apex construction. That, and my go-to electronics guy moved to another city, so I have fewer local resources to tap.

Regardless, I appreciate your advice, and I'm going to take those measurements as soon as I'm back home :)
 
Coincidentally I modded my 460 last night (nothing too fancy, ditched C8 & C9, added a 150pf cap and changed the tube to a NOS 12at7.

My one worry with the construction was accidentally snappy a connection to the pcb/tube, as a few of those don't seem too robust. Take a look and make sure you haven't snapped one off by accident.
 
Some easy ones:

Capsule leads correctly oriented? (which capsule did you use)

Which capacitors? and is it change/remove/what?

I have two of these I'm getting ready to mod (OEM version, and I'm doing the transformer/tube/capsule swap/2x capacitor remove/1x capacitor change/voltage change) mod.
 
p_wats said:
Coincidentally I modded my 460 last night (nothing too fancy, ditched C8 & C9, added a 150pf cap and changed the tube to a NOS 12at7.

My one worry with the construction was accidentally snappy a connection to the pcb/tube, as a few of those don't seem too robust. Take a look and make sure you haven't snapped one off by accident.
Click to expand...

Most mods are with a 12AY7/6072, how do you like the 12AT7? (I've also wondered about using a 12AV7...which has only slightly higher gain then a 12AY7)
 
Watch out for hi voltages

ranjam said:
I hate sounding like an a$$hole (well, not really), but if you are an admitted 'non-savvy' electronics person, you should start learning with a much simpler project. The schematic is out there, and you're going to have to bully your way through it and figure out where the signal goes south. You can start with B+ voltages, and some resistance measurements can't hurt. Your B+ should be on pin #1 and pin #6 of the tube socket, there should be 6.3VAC filament voltage on pin #4/5 (wired together) and pin #9, and you might get 2.7K to ground at pin #3 and 270K to ground at pin #8. After that, a scope and some real troubleshooting chops are needed. The input is pin #2 and the output is pin #8. Good luck, and learn your lesson!
Click to expand...

I agree as far as a simpler project. You can get a bad shock if you are not careful around tubes. Hopefully you have not found this out the hard way. Be careful with the B+ voltage readings! I would strongly suggest that you bite the bullet and take the unit to someone who knows the circuits and as suggested, start with a simpler project to learn electronics. Sorry to sound mean, but I would not make you to make a fatal mistake and without experience with tube circuits, you can.
 
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