Sizzle in Blues Junior at idle

[dude]

I got the amp sounding pretty good after some BillM mods, only issue I had was trouble with one PCB el84 socket, had intermittent popping noises worse when tube was tapped. Re-tensioned pins, went away and sounded good no noises. Now a sizzle, like bacon frying at idle after a hard play, sounds like a bad connection to me maybe that socket is shot, or a tube?
Not looking for a fix here, just am l looking in the right direction?
I really hate PCB, this is the last one l’ll work on.

[Esquirefreak]

Possibly a noisy resistor? I'd pull the PI tube and see if the noise goes away.

If it does, I'd have closer look at the plate resistors for the preamp.

If it persists when the PI tube is pulled, the problem might be in the power section.

[shooter]

all the really important voltages for the PA go through a plug/jack, or did, I quit looking 5yrs ago.
if it's a keeper, hard wire, or do Doug's mod, or grow more hair to pull out

[dude]

all the really important voltages for the PA go through a plug/jack, or did, I quit looking 5yrs ago.
if it's a keeper, hard wire, or do Doug's mod, or grow more hair to pull out

can’t even turn the amp on with a pulled board hanging, can’t do beans on PCB 

[sluckey]

Dude! Drag it to the curb or do Hoffman's conversion if you want a reliable amp.

[acheld]

Sluckey is correct.

But, it is possible that you have burned / damaged the traces on the the tube board -- which is notoriously cheesy and "may" cause symptoms similar to what you are reporting.  These boards can be repaired, but it's not worth the effort. 

Hoffman sells an inexpensive replacement board specifically for this problem (if in fact it is the tube board acting up).   It's a little fiddly to install, but it isn't rocket science.

Overall, though, Sluckey's right.    Hoffman's BJ sounds fantastic, and is very robust.

[dude]

I had low heat, 650*, small point tip, never left the iron on after the melt. Yeah, those small round traces are super thin, like tinfoil. Worked fast with the iron, no traces lifted. It’s not my amp, son in laws, or l would have toss the bd from the beginning. I was having issues biasing, resistance method, getting crazy readings.  Thought it was the 25 ohm difference in OT primaries. But could have been the pin contacts in the sockets. Now l’m getting good voltage drop readings on the plates to OT primary that gets me with 2mAs. The 1 ohm R’s l used on HV, must be off as he current  both ways was way different, so took them out. Amps sounds good except a little sizzle noise when hot.  Pull those tubes in and out, doesn’t take long to rip a pad off. Piece of sh*t. I’m thinking about trashing the bottom tube bd, adding real sockets and get rid of those ribbon cables too.
The sizzle only comes after a half hour of “Smoke on the Water” and “Into the Blue, Out of the Black” ha.
Thanks, when l fix it l’ll post the issue.

[acheld]

I should have clarified what I meant by:

you have burned / damaged the traces on the the tube board

Just playing the BJ causes enough heat to damage that tube board.  Always possible to damage it with soldering, of course, but all three of the BJ's I've owned over the years have had heat related problems with that board. 

The other issue is the ribbon cable, and I've seen cracks develop in the solder connections on both sides of that connection, tube board and primary circuit board.

I like BJ's quite a bit as practice amps, but series I - III suffered from bias issues and heat.   I haven't seen a lot of complaints from the BJ IV, which is now conservatively cathode biased. Maybe (just) Fender figured it out . . .

[scstill]

Would these circuit board and heat related issues also be possible with the Pro Junior?

[AlNewman]

Hi Dude,
From some of the research I've done, perhaps your issue is to do with the plate resistors, especially the ones located under the board where the tubes mount.  Also, I would recommend reflowing all the solder in the tube sockets, and perhaps the ribbon cables and shielded signal lines as well, you need to support these well so they don't move when you reflow the joints.  Another thing I've found, on the HRD at least, is the coupling caps fender used are not rated for the full B+, so if I have the tubes out taking voltages, or if I start up without standby, they are hit with way too much voltage, so I replaced all of them with 630v components.

I'm no expert by any means, but I have been finding these boards are a lot more robust than they're given credit for.  In fact, most issues I've had have been from too little heat, or not giving the iron that extra second after the solder has flowed to get a good joint between the pad and the component.  I also have been using good rosin coated copper braid to remove all the solder.  I don't try to reuse any parts, so I'll cut them off from the top side before removing the wire from the bottom so I'm not putting extra stress on the pads or traces.  If I'm replacing several parts at a time, I'll also clean the pads before I solder new parts in, as well as clean everything after.  Every time I have the board out, I'll check all the connections on the board, and reflow any questionable ones I may have missed the last time I had it out.

I need to force myself to be patient and take my time, whenever I get frustrated I'll just walk away for a few hours or days and it's more of an enjoyable, zen thing than a hassle.  Of course I have the luxury of owning the amp, I doubt a customer would be overly impressed with waiting extra time, but it ends up being a better job, and I learn more as I go.  So far, knock on wood, I haven't had any major problems, and it all still looks tidy and not like a gorilla has been poking around in there with a sharp burning stick.

Check out some youtube videos with computer repair and such, you'll see that those guys really put these pcb boards to the test, and don't have many issues with traces or pads being pulled up.  They just have certain techniques they use, as well as proper tools.  Mr Carlson's lab has some great tips, as well as Psionic Audio, especially applying to the blues jr. and hot rod deluxe. 

Anyways, good luck, and don't stress too much, everything can be fixed, and if not you have a good base for a new build.

[McAbe]

Did you add the BillM adjustable bias? The Blues Jr. is biased super hot. Lowering the bias might help, since it sounds like your issue might be heat related.

[tubeswell]

Another vote for rebuilding it

[dude]

If this were my amp, l would have replaced the PCB with a turret bd. But it’s not my amp.
The sizzle was loose soldered tube pins and loose socket pins. Reflowed solder and retention pins. No sizzle, owner ordered a new tube bd that has through hole eyelets and twice as durable as original, comes with new sockets too, $25 on Reverb.
Amp has bias pot, 26/27 mA bias.
You can’t pull the EL84s too much, loosens the soldered connection on the socket and board, one very cheaply made amp, IMO. Also, grid leak resistors on el84s burn and take the board out, burnt traces. So, an overly biased tube will burn out eventually, draw too much current, take the grid leak out while burning your cheap PBC in that area. Clean the carbon, fix any bridged traces and use 1/2 watt grid leaks.
Then just wait for the next flaw.

[scstill]

Pro Junior (I have 2) are quite similar to Blues Junior (I have none)
For those of you who have rebuilt these to turret board
How much quieter (hum and buzz) did you observe?
I have taken steps to quiet the PJ but still most noisy amp(s) I have
They work and sound good but are noisy when not playing.

Guess I won't know until I try it. So will add to the list of projects

[sluckey]

You can’t pull the EL84s too much, loosens the soldered connection on the socket and board, one very cheaply made amp, IMO.

Have you seen this?

     https://el34world.com/Hoffman/Blues_Junior_Tube_Board.htm

[dude]

You just beat me to it,
https://el34world.com/Hoffman/Blues_Junior_Tube_Board.htm
Had I known Doug made these board, I would have recommended this tube board
 

[acheld]

For those of you who have rebuilt these to turret board
How much quieter (hum and buzz) did you observe?

Very quiet.   Hard to quantify, but I've had no issues.

I have several Blues Juniors -- one stock tweed edition, one MIM used for modding and shop work, and one Hoffman turret board converted to cathode bias.   The Hoffman is the quietest, but honestly I don't find the two Fender models particularly noisy.