12000: Forget step by step I've got a hum

basisfunction · Post by **basisfunction** » Fri Aug 01, 2008 1:31 pm

STEP 1: INSTALLING THE TRANSFORMERS:

Unpack and inspect the transformers and choke. This build assumes you are using the '68 steel chassis from Metroamp. The hole pattern for the OT (C1998) is matched to the Vintage style end bells. You either have to order a set of the vintage style bells or maybe it can come with them preinstalled as an option. You have to email those guys to find out.

Remove the two screws that hold the end bells on. The wax on the surface of the core will most likely hold them on fairly well. Pull hard, or carefully work them off with a regular screwdriver if they give you trouble. Now you're looking at the exposed OT. The Vintage end bells have four outlet holes. Its up to you how you want to route them but I chose the path of least resistance: the primaries and secondaries get one hole each.

Get the bolts loosely installed and the bolts thread. Keep it just loose enough so you can square everything up on the bench and tighten.

Attach OT and PT as in Metro 100 Watt Instructions. PT is little different since its a laydown style. Instead of tabs with holes on an end bell, you put blts directly through the iron and bolt to the chassis.

Attach choke.

I put the grommets in last.

basisfunction · Post by **basisfunction** » Sat Aug 02, 2008 11:53 pm

STEP 2-3-4: :

Step 2: Mount the single surface mount filter cap in its respective bracket. Mount it.

The PI filter cap goes in the same place, the bracket, however, it is smaller (1") to accommodate the TAD or whatever single 50uF panel mount cap you may be using.

Step 4:Install tube sockets, just as in the 100 Watt instructions.

Wicksy · Post by **Wicksy** » Sun Aug 03, 2008 3:09 pm

Looking good so far! I love starting a new amp build!

basisfunction · Post by **basisfunction** » Mon Aug 04, 2008 12:38 am

Yeah!

This thread is redundant and pretty boring right now, I am renovating two bathrooms right now. Pipe in, you guys, when I make mistakes!

Ricky Lee · Post by **Ricky Lee** » Mon Aug 04, 2008 6:37 pm

Pretty much did the same thing here which includes an effects loop and PPIMV as well as international voltage switch. http://www.putfile.com/album/186580

basisfunction · Post by **basisfunction** » Mon Aug 04, 2008 11:18 pm

Yeah, I gottcha. I'm not trying to do anything new. Just journaling my build.

Thanks

Sam

Ricky Lee · Post by **Ricky Lee** » Tue Aug 05, 2008 9:13 am

Great job your doing too!

basisfunction · Post by **basisfunction** » Thu Aug 14, 2008 11:15 am

There are some edits below. I keep saying "Standby off" when I mean "Standby ON"

!

OK. So I didn't have any remaining patience to take pics along the way!
So here it is. Amp sounds pretty decent I should say

... Although, there is a significant hum, especially when the standby is ON. I have seen this mentioned in a few other 12000 threads. My hum is still present when standby is switched to on; This is for either voltage. Although the the hum becomes quieter. Now its not a big deal, but my JTM100 and '69 are very quiet. I am posting a lot of pics for the OCD troubleshooters out there. Maybe there is something wrong.

Notes:

(1) hum is present with no guitar plugged in.
(2) tone controls affect the volume of the hum.
(3) hum is noticeably louder when standby is ON.
(4) its still present when switched to 400V/500V, but is quieter.

harddriver · Post by **harddriver** » Thu Aug 14, 2008 11:31 am

It seems those split turrets can be problematic with cold solder joints because they need so much more heat. Even if you don't have problems now.

Leleduke had major problems and he ended up pulling all the split turrets out and replaced them with Georges standard ones.

Just a thought. Your Amp looks very nice!

From alot of accounts hum problems usually are grounding issues. Retrace all your grounds.

basisfunction · Post by **basisfunction** » Thu Aug 14, 2008 12:52 pm

This seems about right:

http://forum.metroamp.com/viewtopic.php ... =12000+hum

Ricky Lee · Post by **Ricky Lee** » Thu Aug 14, 2008 2:56 pm

Shorten the green wires from the PT to v-7, run them diagonal to v-7; shorten the green/yellow wire to filter ground lug. Also, re-route the DC lamp leads away from under the on-off switch and away from PT as AC/DC don't like company. Recommend twist brown wire with rest of OT wires for noise cancellation.

basisfunction · Post by **basisfunction** » Fri Aug 15, 2008 11:53 am

Thanks!

I'll try these suggestions out.

neikeel · Post by **neikeel** » Fri Aug 15, 2008 1:41 pm

Ricky Lee wrote:Shorten the green wires from the PT to v-7, run them diagonal to v-7; shorten the green/yellow wire to filter ground lug. Also, re-route the DC lamp leads away from under the on-off switch and away from PT as AC/DC don't like company. Recommend twist brown wire with rest of OT wires for noise cancellation.

Beat me to it

Exactly as he says

whopperplate · Post by **whopperplate** » Wed Aug 20, 2008 10:14 pm

Ricky Lee wrote:.... Recommend twist brown wire with rest of OT wires for noise cancellation.

Do you mean twist the brown secondary with the other yellow, green, and black secondary wires?

Ricky Lee · Post by **Ricky Lee** » Wed Aug 20, 2008 10:36 pm

That's correct all get twisted together.