Apex 460 mods ...HELP.

Hi.
So i decided to modify my 460.
Change the transformer to a Cinemag acording to Morph tutorial.

Then i decided to change tube to a ECC81/12AT7.

The only thing i hear now its some kind of a loud pink noise mixed with loud pops.

Any help would be apreciated...i'm a little affraid of tubes...the one i used in there cost me 45$..

Thanks.

Hi,

Change the tube back and test. Then check the wiring and solder joints.

Something weird happened..
Put back the stock tube and it works..
But putting back the Siemens 12AT7 wont work.

Wiring seems to be working...


Weird..

sounds like the tube is bad. try another at7

whats weird is that all tubes i have av7,ax7 only the stock tube seems to work...
Thanks

assuming your replacing the stock tube with a good working tube, then check the wiring...

wiring seems fine 100%...cuz if stock tube placed it works fine.
Now any other tube wont work...12au7,12ax7 even 12ay7...

Stock tube has no markings on it.

Thanks

3nity said:

wiring seems fine 100%...cuz if stock tube placed it works fine.


Thanks

Click to expand...

seems fine and is correct are 2 different things. However if you feel wiring is correct and soldering is good then start checking voltages.... I am pretty sure the tube is a 12ax7 china or maybe a 12at7 china. either or will work in the tube socket if the voltages are correct.  

yeah...you're right.
Now what should i look for? to high voltage?

Thanks

Start by checking for your heaters then check your plates....

here is the schematic


http://www.apexelectronics.com/downl.../smapex460.pdf

most of those 12A tubes should sub for each other in a pinch
just with gain & impedance penalties
As someone mentioned take a KNOWN working tube from
say a gtr amp and throw it in there
is there something physical about the tube ?

Alright.
Bad tubes...
Found another 12AT7 Tung sol in working condition.
Fortunately i bought the Siemens 12AT7 locally.

Thanks

3nity said:

Alright.
Bad tubes...
Found another 12AT7 Tung sol in working condition.
Fortunately i bought the Siemens 12AT7 locally.

Thanks

Click to expand...

Nice... care to comment on the sound now with an upgraded tube and cinemag transformer? On my 460's I changed the tube to a 6072/12ay7 type. After all it is a c-12ish type design. I also changed the transformer with some jensen's I had lying around. talk about an upgrade. It sounds more usable to me now then before. I kept the stock capsule and did not change any caps although there is web traffic where people talk about it. I am not so convinced on that as currently I like the over all sound they have now... So why bother right?

you can do endless mods on that mic. I wouldn't care about caps before getting a better capsule. If you have the cash, get a tim campbell ck12.
nicholas

Pucho, what Jensens did you use?

I've got a non-functional 460 I bought on this forum a while back, sitting in my garage...

It's worth it to change C8 to a film cap, if your mic has an electro in that spot connecting to the output transformer.
Still need to do the transformer switch on my Nady 1050, but with a 12AT7 and a decent film cap in C8, it can sound very nice, especially in omni...

Hey just wanted to say that I had a couple tubes I thought were bad...

I just needed to clean the pins! I cut off a piece of scotch-brite pad and gently cleaned off the corrosion on the pins, then all was well. Then I used one of the Caig sprays on the pins to protect them.

tommypiper said:

Pucho, what Jensens did you use?

I've got a non-functional 460 I bought on this forum a while back, sitting in my garage...

Click to expand...

I had some jt-115K- that came off an old MCI channel strip that was being junked...  they are 1:10 Pri:Sec that I wired backwards as a 10:1. works great.

I just needed to clean the pins! I cut off a piece of scotch-brite pad and gently cleaned off the corrosion on the pins

Click to expand...

Actually the rest of tubes have all pins have corrosion..
Nice thing to do.
I'll try that...

Thanks