86-Special ready with noise problem

[Tillydog]

Another question: I have two speaker jacks 4 and 8 ohms. How could I insure not to have an open circuit (no speaker connected) with those two jacks ? A 270 ohm resistor between + and - on both of them ?

Just one resistor should do it (I would put it on the 8 ohm tap, but I don't think it matters much).

I don't know about screening the OT secondaries - I doubt it would help, but you never know.

Any chance of an updated gut-shot?

[mat]

Another question: I have two speaker jacks 4 and 8 ohms. How could I insure not to have an open circuit (no speaker connected) with those two jacks ? A 270 ohm resistor between + and - on both of them ?

Just one resistor should do it (I would put it on the 8 ohm tap, but I don't think it matters much).

I don't know about screening the OT secondaries - I doubt it would help, but you never know.

Any chance of an updated gut-shot?

Actually the the OT secondaries are 8ohm and 16ohm (wrong labelling on the back panel) I'll put the 270R on the 8ohm.

I don't have yet the shield/cover. After rerouting the wires I have new noise issues. A constant but volume-altering white noise (bit like ocean waves to the shore) and ocassional pop corn effect. I will reflow every new connections.

I'll take new pic asap.

[martin manning]

I just posted up a solution for no-load protection when using separate speaker jacks in this thread: https://tubeamparchive.com/viewtopic.ph ... 223#267223

[Tillydog]

After rerouting the wires I have new noise issues. A constant but volume-altering white noise (bit like ocean waves to the shore) and ocassional pop corn effect. I will reflow every new connections.

Yup, that sounds like a bad solder joint somewhere....

(Neat circuit, Martin)

[mat]

I did reflow the new solder joints and put a pcb sheet to cover the chassis. Still got some noise ocasionally (only 3 times during 5 hour playing session). When the noise came I tried to slap the amp but it did not affect the problem.
So it might not be a loose component.
The noise (popcorn style) came in and then after a while a few pops and then it dissappeared.
The od-channel has a problem also. Adjusting the volume pot from zero it jumps immediatly at very high level. Have to check the pot connections. Also the gain pot acts more like a volume pot and at full it gives very little overdrive comparing to the little brother amp (same preamp) I built.

I need more free time and less wokr hours..

I'll take new photo asap.

[Structo]

Could be a faulty pot.
I had a input volume pot that jumped like that, just disconnect the pot and put your ohmmeter on it and rotate it slowly to see if it is smooth.

[mat]

Could be a faulty pot.
I had a input volume pot that jumped like that, just disconnect the pot and put your ohmmeter on it and rotate it slowly to see if it is smooth.

Thanks for the tip Structo, I'll try that tomorrow. Might be also related to the noise problem I'm having. The noise reminds little bit of a wind and then it gets louder and after few louder cracks and pops it stops. This happened quite a bit at the band rehearsals today. Noise goes away when turning the clean volume pot to zero. Also I think it lessens with the bass pot at zero.

I changed the drive pot wiring (output at the wiper) and now it gives more drive.

This is a really loud light weight tiny amp. This will be my gigging amp if I will ever get rid of the noise problem..

Any other tips of nailing the noise problem ? Anyone else had this hiss and then few cracks and pops. What was the cause of the problem ?

Few fresh picks of my ugly build: http://www.flickr.com/photos/fuzzface19 ... 096864875/

[Tillydog]

The noise reminds little bit of a wind and then it gets louder and after few louder cracks and pops it stops.

My earlier comments were based on it being a constant hissing noise, as you would get with HF oscillations, so if it has always been like this, then I've sent you on a wild goose chase - sorry!

To me, those are cast iron symptoms of a poor connection (likewise the 'popcorn' description).

It could be inside the pot;

It could be a solder joint;

It could be a cracked resistor;

It could be a dirty tube socket or pin;

It could be a bad contact inside one of your switches/relays;

It could be bad contacts on yout FX loop jacks;

It could be a bad tube, etc... etc...

As it is intermittent, it'll be a bitch to track down

It's best to critically examine every solder joint and clean/remake any that are suspect, rather than blindly re-flowing them (not saying that's what you're doing).

You could try bypassing the FX loop jacks to eliminate their contacts.

It sounds like it's well worth changing that dodgy pot early on...

Also you could cleaning up/tensioning the tube sockets & cleaning the tube pins.

You could check that you still get the noise with each switch in all available positions - it would be especially bad luck to get one that was noisy in both positions (suspect your channel switch/relay if you're not getting as much volume as you would expect from one channel). Maybe try hard-wiring the switch terminals as a diagnostic exercise.

I can't make enough detail in the photos, sorry.

If you have freezer spray, it's sometimes useful in pin-pointing this sort of thing, but I would keep it away from the tubes.

Good luck :-/

[mat]

The noise reminds little bit of a wind and then it gets louder and after few louder cracks and pops it stops.

My earlier comments were based on it being a constant hissing noise, as you would get with HF oscillations, so if it has always been like this, then I've sent you on a wild goose chase - sorry!

Sorry Tillydog, I should have said more clearly. This is a new kind of noise problem. First problem was constant that I got almost complitely rid of with the pcb-material shield. The new one is volume altering his/popcorn.

To me, those are cast iron symptoms of a poor connection (likewise the 'popcorn' description).

I will check/reflow every suspect connections.

It could be inside the pot;

It could be a solder joint;

It could be a cracked resistor;

It could be a dirty tube socket or pin;

It could be a bad contact inside one of your switches/relays;

It could be bad contacts on yout FX loop jacks;

It could be a bad tube, etc... etc...

I think I'll start wit a new set of tubes. The EF86 should not be the bad one because the problem exist also on the clean channel. I'll change the V1, PI and EL84's (have to buy a new pair).

As it is intermittent, it'll be a bitch to track down

Yes, it seems so

You could try bypassing the FX loop jacks to eliminate their contacts.

It sounds like it's well worth changing that dodgy pot early on...

Also you could cleaning up/tensioning the tube sockets & cleaning the tube pins.

You could check that you still get the noise with each switch in all available positions - it would be especially bad luck to get one that was noisy in both positions (suspect your channel switch/relay if you're not getting as much volume as you would expect from one channel). Maybe try hard-wiring the switch terminals as a diagnostic exercise.

Every part I used on this build are new. The tube sockets should be ok as the other components. I'll start with the tubes and go to the solder joints after that.

I can't make enough detail in the photos, sorry.

Sorry, lousy iPhone pics..

If you have freezer spray, it's sometimes useful in pin-pointing this sort of thing, but I would keep it away from the tubes.

Don't have a freezer spray, hope I'll catch the problem before I need that.

Good luck :-/

Thanks

[Tillydog]

Every part I used on this build are new.

That's not much of a guarantee on some jack sockets!

(Likewise, switches, pots, etc. can get 'cooked' during soldering and give problems after)

[mat]

Every part I used on this build are new.

That's not much of a guarantee on some jack sockets!

(Likewise, switches, pots, etc. can get 'cooked' during soldering and give problems after)

I think You are right.

One thing I noticed today that the noise went away when turning the bass pot
to zero and the noise went worse when engaging the boost switch. Hope to have time tomorrow to purchase new pair of EL84's.

[mat]

Ok, did change every tube except EF86 - no fix. Reflow few more connections - no fix.

I turned bass pot to zero - no noise. Changed the 500kB bass pot and the 1n cap to new ones - no fix.

Now when I engage the boost -> no noise ?? Argh!

Back to troubleshoot..

[mat]

Changed the PI tube socket. Redid all heater wiring (much neater).
Reflow more than dozen joints. Changed 3 caps on turret board. Examined with magnifying glass about 2 hours. Redirected couple of PI and power section wires.

No help yet..

Back to troubleshoot.

[Tillydog]

Bummer!

If you can get some nice, big, clear pictures I'll have a look, too.

[mat]

Bummer!

If you can get some nice, big, clear pictures I'll have a look, too.

Thanks Tillydog ! I'll take the chassis to work today. There I'll get better lighting.

One PITA is the ready made turret board. It is really hard to solder on that one. This is the first ready made I have used. I talked to the seller and he said he pre solders the turrets before soldering in the components. I heard it is from China. Earlier (and for now on) I've made my boards with american turrets.

Pictures asap..