The Start of a Plan

[jamaio]

Probably just a coincidence. There are three jumpers on V2 socket. Are these jumpers soldered securely and on the correct pins?

Yes, the pins are correct, however, I plan to redo the wiring there. I may bring a tone generator and a scope home from work Monday. When I first turn the amp on there is no sound until I jump the pins. I would like to use the scope to see where the signal stops. Could it be a bad solder joint that is overcome by jumping the pins?

Once I know where the signal stops I should be able to find the problem

Thanks for your reply.

[sluckey]

When I first turn the amp on there is no sound until I jump the pins.

"Jump the pins"... What does that mean? Those pins should be permanently jumped. Kinda like this...

[jamaio]

When I first turn the amp on there is no sound until I jump the pins.

"Jump the pins"... What does that mean? Those pins should be permanently jumped. Kinda like this...

When my meter lead slipped it made contact between pin 2 and 3 just for a second, then I heard sound, the amp will then play until I turn it off. Once the caps bleed down and I turn the amp on again, no sound again until I momentarily jump pin 2 and 3 again. Before jumping the pins I do get very low sound if I crank the master and volume to 12.  Later today I will go over the wiring at V2 again to make sure everything is good, it looks like the picture but I want to check everything.

[jamaio]

Well I have finally fixed my amp!! Thanks for all the help and replies to my crazy posts.

So my last symptom was very low output volume and no treble, mid or bass tone control. I had gone through everything several times to fix all the other issues I had so I was confident that everything was connected as it should be. The last problem started after I installed the chassis back in the cabinet. It worked fine on my bench and sounded great, so what happened??

I went back to basics and started checking voltage everywhere while injecting a 1004 hz tone at 0 db. When it came time to check the voltage at pin 2/7 on V2, with one meter lead on ground, as soon as I touched the other lead to pin 2/7 on V2 I had normal volume but no tone control. I only had to touch the lead for a second for the volume to increase. The volume would slowly decrease as if a cap was bleeding off, so it appeared the meter was supplying ground to energize the circuit. I had been checking my connections at V2 because I had a problem with wiring there that caused my initial hum problem; so all my focus was on that side of the chassis. After rewiring V2 again the problem still occurred so I started looking other places. When checking voltages at the tone pots I found the ground wire at the mid pot broken, it was as if the wire snapped in half, it appeared to be connected but under a magnifying glass I could see the break. This ground is where the treble and bass get their ground from so that explains why I had no tone control. I replaced the ground and everything works again. I was ready to chuck the whole thing in the garbage and start over but I was determined to find the problem. I am glad I can put this one behind me and move on to my next project.

I learned a lot from my first build, check everything several times before moving on to the next phase. Don't solder any connections until the layout is complete and checked at least 3 times. Once everything is soldered check it again before turning on the power.

Thanks again for all the help.

[whoops]

I have a Blues Jr. that I will be converting with the Hoffman kit for my first project.

I was considering a second project.

Relax

I ordered all new replacement caps from Doug, I do not trust the condition of the caps with all my mistakes.

Calm Down

I was ready to chuck the whole thing in the garbage and start over

Chill Out,
with what you described it's was obvious you had an "intermittent connection" problem, I was going to tell you that but you never replied to my questions...


Being successful in completing projects and troubleshooting requires Patience.
You seen to have the technical skills needed, now just you need to improve the relaxation part!
Other people are quite relaxed but have no skills

[jamaio]

with what you described it's was obvious you had an "intermittent connection" problem, I was going to tell you that but you never replied to my questions...

Sorry, I missed your questions. I had connected an electrolytic cap backwards and I was concerned that I fried it. I thought maybe I was losing volume due to a short to ground (blown cap), so I wanted to trace the signal path to see where I was losing signal, that is when I discovered the anomaly that would give me volume until the caps bled down. I just had to wrap my head around what was happening so I could figure it out. Finding an open ground in a circuit with caps is different than a circuit with no caps. And since I made so many mistakes I was starting to wonder if I did something wrong again, I had to think back, it worked perfectly on the bench, what changed when I mounted it in the cabinet.

I am calm, believe it or not, I write with enthusiasm to make the topic more interesting, I do not want to bore everyone with dry posts.

I promise I will be better for my next build, I have read so much on the forum and I am familiar with the layout of the turret boards now so the next one will be a lot smoother.

Don't try this at home kids, it's dangerous!!!

Thanks for sticking with me until the end!!

[purpletele]

So what is next??

Hoffman's shop is still open

[jamaio]

So what is next??

Hoffman's shop is still open

Haha!!  If you saw the beginning of this post I have the first amp I bought back in 1995, it's a Fender Sidekick Reverb 35 1x12 combo, solid state made in China. I plan on using it as my starting point. I am considering a Stout Reverb although the reverb tank is 16.75 inches long and the cabinet I have is about 15 inches wide. I may have to strap the reverb tank to the back of the amp or get a smaller one. I do have the reverb tank from my Blues Jr. that I could use.

I should be ordering more parts soon!!!

[purpletele]

I just completed the Stout which is a cool amp.  Check out the Blackheart 5 Conversion.

I haven't looked at the Stout Reverb closely, but I thought that it is just a Reverb effects amp.  Is that what you were after?

I also put the 18 watt Plexi into a Blues Junior chassis and custom case.  That is a spectacular amp that we are tuning up now.

[jamaio]

I haven't looked at the Stout Reverb closely, but I thought that it is just a Reverb effects amp.  Is that what you were after?

I want to do an amp with tube reverb, as you know the Blues Jr. had reverb before the Hoffman conversion, or I may just wait on a second build and add tube reverb to my Blues Jr. I usually don't use and pedals, I have a tube screamer but never use it. I did just buy an iRig 2 and I have been trying out the free pedals that come with the software. I just play to entertain myself in my house, not looking to become a rock star!!

I will have to check out your builds!!

[whoops]

it worked perfectly on the bench, what changed when I mounted it in the cabinet.

Normally from bench to chassis these can happen:

- A wire connection breaks
- A connection can become loose,
- A component breaks
- you have one more ground connection
- you have one less ground connection
- More Hum, and More interference
- Less Hum , and less interference
- you left an aligator clip connected to the circuit, and it's loose inside now
- wires changed the relative positions to other wires
- you forgot the solder roll, the soldering iron, one screw, your marriage ring or your phone inside the chassis


You were lucky in your situation as it was the most common scenario.

[jamaio]

I finally have my Blues Junior dialed in, after adding and removing mods I settled on the original Hoffman layout with the Sven Ericsson mods Doug posted here:
http://el34world.com/Forum/index.php?topic=17991.msg182188#msg182188

I also added an Eminence Cannabis Rex speaker.

The end result, the bass is very tight and punchy, the highs sing and have a very good tone and the amp no longer sounds boxy.

I hope to have sound clips soon with a side by side comparison of a stock Blues Junior.