New to forum-just bought a 36 watt

flatfive · Post by **flatfive** » Wed 04/30/08 5:02 pm

So I got this amp on eBay. I think it may be too clean, but I want some feedback. It was built with a layout supplied by this forum. It has a master volume, but I can't get any gain out of it. I may need to make some changes. I'll post the chassis pics one at a time. I recently built a 5e3, but really don't know much. Thanks.[/url]

flatfive · Post by **flatfive** » Wed 04/30/08 5:05 pm

The MV is on the back where the impedance switch goes. It really doesn't do anything.

flatfive · Post by **flatfive** » Wed 04/30/08 5:46 pm

Actually, I jumpered the two channels and started to get some gain but not overwhelming.

sub · Post by **sub** » Wed 04/30/08 6:02 pm

Hi flatfive,
Your amp is loud? (i mean very loud

)
Are you tried on full volume?
What speaker(s) do you using?

Post by **jaysg** » Wed 04/30/08 6:53 pm

Did someone on this board make it? Ceriatone kit or other? I don't like what I see with the Xicon cement power resistors touching each other. Probably fine, but they shouldn't touch.

flatfive · Post by **flatfive** » Thu 05/01/08 12:29 am

It may be built by someone on this forum. The seller did mention this forum but didn't actually build the amp. I probably should have built it on my own but the price was right.

Yes, the amp is very loud and I haven't had a chance to really crank it yet. I didn't think you had to dime these amps to get them to distort. I have a bunch of Fender amps that are that way and you have to use pedals. I really like the sound of the 18 watters I've heard.

Anyway, I thought someone might see something wrong. I will probably search the forum for half power switch info. I have trouble with schematics, so I need a layout of some kind.

flatfive · Post by **flatfive** » Thu 05/01/08 12:35 am

The speaker is an unknown Alnico speaker (not Jensen) from a tube organ. The code is 12JB-89 465-213. It has Heyboer trannies and an 18 watt TMB circuit.

flatfive · Post by **flatfive** » Thu 05/01/08 12:50 pm

Those 1k 5w Xicons don't fit any of the schematics I've seen. I have a Richie Hall layout that shows 130 and 100 ohm resistors there.

TDuly · Post by **TDuly** » Thu 05/01/08 2:22 pm

The layout that was used is the revision 5 but it appears he didn't use the push pull bass pot to defeat the tone stack. The 1k 5 watt power resistors are correct. It appears that your master volume control is wired incorrectly though. From the photos it seems like the feed is coming off of the bass pot rather than the treble pot as shown in the revision 5 layout.

Also the treble and bass pot connections with the yellow wire are on the wrong terminals. Your problems seem to be mostly in the tone control wiring as I see more than one miswire.

Go to the downloads section and get the revision 5 layout to check your wiring. If you can't read the eps version, attached is my 5b version which is similar.

This amp is very loud and gainy so after you have fixed it you are going to want an aluminum shielding plate under the chassis (if this is a head version) as it will pick up waves from the speaker cabinet below and squeal like a pig otherwise. Wired properly this is a great amp. Too bad you don't have the push pull bass pot. Taking out the tone stack really adds a different tone to the amp. You might want to consider putting that in after you get it working.

morcey2 · Post by **morcey2** » Thu 05/01/08 3:27 pm

flatfive wrote:The MV is on the back where the impedance switch goes. It really doesn't do anything.

I'm pretty sure that's a Negative Feedback switch, not an impedance switch.

Matt

flatfive · Post by **flatfive** » Thu 05/01/08 3:59 pm

Thanks, TDuly.

Post by **jaysg** » Thu 05/01/08 4:06 pm

Click on the last pic to the right -- is this your rear panel?

http://www.ceriatone.com/productSubPage ... 36watt.htm

flatfive · Post by **flatfive** » Thu 05/01/08 4:13 pm

Nope. This is my rear panel. Where do you get the push-pull bass pot? AES has a Fender one.

TDuly · Post by **TDuly** » Thu 05/01/08 4:35 pm

The switch on the back panel is definitely a negative feedback switch but there is a master volume pot where the impedence switch should be.

It appears that only one secondary wire from the OT is wired at the jacks. The OT secondary wires appear to be orange, yellow and green and the green one appears to hit the first jack on the right and then jump via the blue wires over to the second jack and then on to the negative feedback switch. I'm assuming the green wire is the 8 ohm tap and that the two jacks are wired in parallel. The other two secondary wires appeared to be heat shrunk off. I'd find another place for that master volume pot and put the impedance switch back in as it adds speaker cab versatility. You could put the master volume pot in place of the B+ HT fuse and put that fuse inside the chassis then put your impedence switch back where it belongs.

As far as the push pull pots, I get mine from Hoffman Amps but he is out of stock on the 1 meg push pull at the moment:

http://www.hoffmanamps.com/MyStore/perl ... =467170043

I know you said you have trouble with schematics but here is the one I edited to represent my Rev 5b. You will notice some different value components from yours as there were some tweaks after the initial layout. I have a thread on page two of the 36 watt forum that chronicles the changes.

flatfive · Post by **flatfive** » Thu 05/01/08 5:59 pm

Thanks again. Yes, they hard-wired it for 8 ohms, but this is a combo amp anyway. I did notice the 330k resistors are 470, so that's probably wrong.

How can I try disconnecting the tone stack to see how I like it before getting the push pull bass pot?

TDuly · Post by **TDuly** » Thu 05/01/08 7:13 pm

Even if it is a combo amp you could have a second external speaker cabinet of the same impedence (8 ohms) plugged into the parallel speaker jack and set on the other side of the stage for great room coverage. Set your impedence to 4 ohms with them both plugged in and your good. Or you could make a stack with a different model speaker to expand your tone. Versatility

All you have to do to simulate the push pull switch is lift the ground connection of the middle control. That's what the switch does.

Make sure you check every connection and component against the layout. The 330k's are a mod to the original. The 470k's will work though. There are a couple of other component mods too. I like the way the amp sounds with the component value revisions in the layout I posted. Post if you have any problems, but best advice is triple check everything.

Post by **jaysg** » Thu 05/01/08 7:19 pm

flatfive wrote:Thanks again. Yes, they hard-wired it for 8 ohms, but this is a combo amp anyway. I did notice the 330k resistors are 470, so that's probably wrong.

How can I try disconnecting the tone stack to see how I like it before getting the push pull bass pot?

I hope you mean 470K.

Disconnect the wire from the mid pot to ground.

flatfive · Post by **flatfive** » Thu 05/01/08 8:57 pm

I tried disconnecting the ground from the Midrange pot and I got nothing but cleans out the amp. The MV still worked, but I couldn't get any overdrive at low volume even with the channels jumped and volumes on 10.

So I put the ground back on and now I at least have something. I really can't find anything wrong with the chassis other than a couple of small resistor changes. I guess this amp just has lots of headroom. I do like it, however. Compared to the 36, my Deluxe Reverb sound like a small amp with not enough bass. I'll stick my OCD on it and give that a try.

TDuly · Post by **TDuly** » Thu 05/01/08 9:53 pm

flatfive,
have you corrected all of the wiring errors in the amp? There are quite a few and things won't be right until you fix them.

flatfive · Post by **flatfive** » Thu 05/01/08 11:48 pm

Yes, I think so. The pots were wired correct after all, they had the treble on the left and the bass on the right and the layout had it the opposite. I couldn't find any other problems.

Donations

Links

Welcome

New to forum-just bought a 36 watt

New to forum-just bought a 36 watt