Herbert Channel 3 - fuzzy/troubleshooting

[nbarts]

I've tried a few preamp tubes for V2 & it sounds fuzzy. Should I order some more tubes & keep trying? Do I need some special tube for V2? Channel 1 & 2 sound like they are supposed to sound. Anything other than V2 tube that can cause this?

 

[Peter Diezel]

12AX7A-C highgrade

 

[nbarts]

12AX7A-C highgrade

Any particular brands?

 

[Peter Diezel]

The manufacture is Shuguang from China.

They are distributed by Ruby, Doug´s tubes, etc

 

[nbarts]

Just ordered a new set of preamp & power amp tubes, hopefully it will fix the problem.

 

[nbarts]

Just installed a new set of highgrade preamp tubes, SED EL34s & rebiased the amp. Did not fix the problem.

I guess I'll have to ship it to Salwender, but this is REALLY NOT a good time for it.

Will it harm the amp if I keep using 1st & 2nd channels until I have the time & finances to ship this thing back & forth? I pretty much never use ch3 anyway.

 

[Peter Diezel]

Since when the problem occurs on channel 3 ?

 

[nbarts]

Since when the problem occurs on channel 3 ?

I week before I started this thread.

 

[Peter Diezel]

I would replace the two 22µF/500V caps

 

[nbarts]

I would replace the two 22µF/500V caps

Hi Peter,

Thanks for the reply. Is this easy to do? Can my local tech do this? Where can I get those caps?

 

[Hey_bert_whtcha_doin_bert]

Hey dude,

If you remember my thread, that's what I did. You can get them from Parts Express if you want to do it yourself. A tech could do it no problem. If you want to do it yourself it's not really hard but you MUST be careful, they pack a punch if you ground yourself out. If your not an ace at soldering don't try to de-solder them from the board, instead cut the leads and twist the new cap leads around the old leads then run some solder over them(MAKE A NOTE OF POLARITY). It would be a good idea to get some silicon caulking(type II(2) ONLY!!!) to put under the caps to give them some cushion from vibration. If you can't get new quick ties in there don't worry, they're not entirely needed, but if you want or are worried, run a healthy bead of silicon across the top of the two caps. Take a look at my old thread, unless the caps look swollen or have electrolyte seeping out they probably aren't bad, also if they are bad it would be more hummy than normal, although they may have been on their way out when you got the head. I'll put a link to my old thread after I get done writing this.

Later on,

-Nick

edit-a-rino:http://www.rig-talk.com/forum/viewtopic.php?f=14&t=33961

 

[Peter Diezel]

Thanks Nick

 

[nbarts]

Thanks Nick,

OK, this can be something different. I've noticed ch2 is weird too, it is not as fuzzy as channel 3, but it's definitely not alright. I didn't have much time to check things today, but I will do some testing & see what's what.

Edit: Nick, I've just noticed you had weird noise on Ch2 also, just like me. Seems pretty similar. I'll make a clip today or tomorrow & take the amp out of the cabinet & see if I can see anything visually wrong inside. I believe this may have something to do with overheating.

 

[nbarts]

OK, here is an mp3, condenser a few FT away. Channel 1, then ch2 -, +, - & then around 1:05 you can hear channel 3. Channel 2 gain is at 9:00, in minus position it should be clean. I flipped the amp & I couldn't see anything visually wrong with my naked eye. I'll take some pictures & post them soon.

 

[nbarts]

Here are some pics. If there are any other pics I can take to help understanding what's happening, don't be shy to ask...

http://www.dizero.com/studio/pic.zip

 

[Hey_bert_whtcha_doin_bert]

This cap is bad, it has leaking electrolyte, I need a better picture with better lighting for the other two. A chinese manufacturer stole an incomplete electrolyte formula and flooded the market with bad caps a few years back, they're still being weeded from the market, more than likely this is the case. Computers got hit really bad with the defunct caps. As far as the mp3 it sounds similar but a little worse than what mine sounded like, more than likely a settings thing. Did the bass roll off some? If it did then this is most likely your problem. Anyway it goes you definitely have to replace the one cap, you will notice some sort of improvement even if it isn't your cure, definitely less hum. Need better pics of the other caps.

Later on dude,

-Nick

Edit: By the way, definitely NOT a heating issue, the Herbert boards are too well built for that.

Edit 2.0:

Here's the two caps I need a better pic of and in the pic you can see a bad cap and a good cap, there shouldn't be expanding goo/foam coming out of the lead area.

 

[nbarts]

Thanks a lot!

Just took some better shots
http://www.dizero.com/studio/pic2.zip

To me it looks like the one on the top/right needs to be changed too.
The bass did roll off some & the whole thing sounds weird, that's not at all what Herbert sounds like.

This is what I need to replace them with, right?
http://www.partsexpress.com/pe/showdetl ... er=020-668

 

[Hey_bert_whtcha_doin_bert]

Replace.

Yes, that's the ones.

Later on,

-Nick

 

[Peter Diezel]

Any news ?

 

[nbarts]

Any news ?

I've placed an order for caps today, I'll have them probably in the beginning of the next week. I'll keep posted.