Revibe Build

[EKDENTON]

So I looked at what reverb units I could build and decided to do a head type with controls facing forward rather than the controls on top of the enclosure like the traditional fender reverb. I decided that Sluckey's Revibe would be the best for what I want. So far I have the turret board made, and almost finished populating. I lack a few parts that I had to order. I made a mistake and thought the schematic on Sluckey's website was Doug's schematic so that led me to order parts off Doug's BOM. That was not correct because the PS's are different. So I had to order a few more parts for that also. So far other than getting used to the spacing of the parts on the board being tighter than I make on my own turret board designs I have not had any problems. I really like the SS rectifiers that Doug Sells, wish all his resisitors didn't come mixed together in one bag though. The color bands are very hard to tell what they are, most of the colors look brown or black to me. I had to measure each one to find the one I needed.....and the one I needed was always seemed to be the last one in the pile.....LOL.

[sluckey]

I see an error with the jumpers on that board. Once I spotted that I quit looking. Thought I'd give you a chance to find it. This is a good opportunity to click on the link in my signature at the bottom of this message and trace it out.

I think you'll spot it pretty quickly and also be able to verify everything else is correct. I won't leave you hanging long enough to get frustrated. 

[kagliostro]

I've find it in a very small time (Happy about)

But I din't wanto to deprive you of the satisfaction to find out for yourself

Only is something that stay on the left instead of the right 

Ciao

Franco

[EKDENTON]

Okay I see it, to the right of the rectifier I was off by one turret. It's what happens when you stay up too late working on one.

[sluckey]

Bingo!

[EKDENTON]

Got my chassis sheared out and the corners notched for folding. I sheared the .090 5052 aluminum sheet 23-1/2" x 11-1/2". Once folded it will be a finished size of 17" x 6-1/2" x 2-1/2" with 3/4" ears turned out on the ends for fastening to the cabinet. I probably will shelf the chassis until I finish the turret board. Then I will lay everything in and on the chassis and double check how well everything will fit then mark what goes where with a sharpie. That way I don't get things reversed and punch holes on the wrong end of the chassis.

[EKDENTON]

Made some progress on the Revibe. I finished the chassis, checked to make sure all the parts would fit, punched all the holes and have almost all the parts mounted. I still need one switch. I noticed the layout I am building from has the power switch on the back side of the chassis. I rather have mine in the front with the other controls. I will put it left of the speed switch.  I found an old abandoned Carvin footswitch with two switches that I can modify to work just fine. By mistake I made the turret board smaller (my printer printed it 9-1/4" wide and it should have been about 12" wide but it will still work just fine. A few of the parts will be a bit snug. I adjusted my cnc router toolpath, and removed the space where the 22uf cap would have gone with the original power supply so the next turret board i cut will be the perfect size.

[EKDENTON]

A couple more pictures.

[NO_H2O]

That is looking very nice.

[labb]

you might like this one...6G15, With help from this board

[EKDENTON]

Very nice.

[EKDENTON]

Sluckey on your revibe is the vib footswitch RCA jack actually on the opposite corner from the turret board hook up point? Checking to make sure that they did not get moved closer together. Also another question the reverb and vibrato jacks do not show any grounding, do they just ground through the chassis? Two of the RCA jacks Doug sent without washers with the hookup hole so those two jacks do not need them?

Okay never mind I see in your photos what you did.

[EKDENTON]

I finished wiring the revibe this evening and I am having some issues with it. I am not sure exactly how this thing hooks up but I have my guitar in the revibe input, then a guitar cord from the revibe output to the amp input. With the revibe turned off and only the cord from the revibe to the amp plugged in, I am getting hum. when I switch on the revibe I am getting loud buzz and no guitar sound at all when the guitar is plugged in.

I checked voltages before trying it out and here is what I have:
B+ 263vdc
V1:
1. 148.9
2. -0.04
3. 0.642
4. 3.02vac
5. 3.02vac
6. 191
7. 0.01
8. 0.04
9. 3.02vac

V2:
1. 100
2. 0.00
3. 1.25
4. 3.02vac
5. 3.02vac
6. 148
7. 0.04
8. 0.03
9. 3.02vac

V3:
3. 252
4. 257
5. .02


V4:
1. 214
2. -1.17
3. 2.02
4. 3.02
5. 3.02
6. 207
7. -0.39
8. 0.04
9. 3.02

V5:
1. 172
2. -0.3
3. 1.23
4. 3.02vac
5. 3.02vac
6. 244
7. 0.08
8. 4.72
9. 3.02

[tubeswell]

With the unit plugged into an amp, do a pop test on each grid - starting from the stage closest to the output end of the revibe's signal path.

[sluckey]

Your B+ seems low. Which PT did you use? I also see several tube voltages that indicate problems. For example, V1 pin 8 should be about 1.5v. Your voltage indicates V1B is not working. And same with V2 pin 8. And V4 pin 8 is wrong also. In fact, V4 pins 3 and 8 should be connected together, but you show different voltages???

You need to double check your wiring. Did you forget to connect pins 4 and 5 together on the little tubes?

Looks like you followed my schematic, board, and chassis layout. OK, let's divide and conquer. Remove all tubes except V1 and V4. Set the mix pot all the way CCW. This should be dry signal only. The signal path is input jack to V1B to V4 to output jack.

Plug guitar into the input jack and plug the output jack into an amplifier input. You should be able to get a normal dry guitar signal into your amp with no hums or buzzes. There will be no effects.

Tell me what symptoms you have with this minimal setup.

[EKDENTON]

Okay with tubes 1, 4 still in dwell all the way CCW same issues occur.

[sluckey]

Okay with tubes 1, 4 still in dwell all the way CCW same issues occur.

That should be MIX pot set to max CCW. Continue troubleshooting with just V1 and V4 until you get a clean guitar signal through the unit. First step has to be verify wiring. Click on the link in my signature line in this reply for a good method to verify schematic, board, and actual amp wiring all agree.

[EKDENTON]

Sorry yes when i checked it I had all the pots set CCW. All parts including Transformers i ordered off of Doug's BOM. Let me double check on V4, I did see that,  and I tied those cathodes together. I will double check that. I thought that was odd when i took voltages, maybe i did not have the the test pin on my meter in good contact with pin 8. When i print the schematic and the layout my printer prints the lines very light so they are difficult to see. Let me try to trace the signal.

[sluckey]

One big concern I have is your B+. You should have about 330vdc directly on the positive terminal of that bridge rectifier. And there should be 260VAC between the two PT red leads. What do you actually have for these two readings?

[EKDENTON]

Testing with V1 and V4 tubes still in I'm getting 248vac on the secondary winding and a B+ is 330vdc. The PT IS A  Mojo 779 HT6190-1. I rechecked voltages on V4 3&8 and they are the same at 3vdc.

[sluckey]

Testing with V1 and V4 tubes still in I'm getting 248vac on the secondary winding and a B+ over 330vdc.

That's better. Initially you said your B+ was 263V. But that was with all the tubes in. The 6V6 is the only current hungry tube, but it should not have dropped the B+ that much. Makes me think there's something wrong in the 6V6 circuit or that PT is just not up to the task. I've never seen any voltages for the Hoffman revibe with that Mojo PT, so I don't really know what's the norm. You may have noticed that my PT came from Weber. I chose it because it was beefier than the Mojo PT. Maybe Doug can post the voltages on his revibe with the Mojo PT?

Let's put a pin in it for now. You have other issues that need to be corrected. Have you verified that everything is wired correctly and that the component values are correct? I think it's time to post some hi rez pics of the inside of the amp.

PS... I have my revibe on the bench now so I can easily make comparisons to yours if needed. Just let me know.

[EKDENTON]

Working on tracing with a highliter now. Will see if I can work through it. I

[EKDENTON]

I highlighted and checked the wiring. On the schematic. I had a 680 ohm resistor rather than a 680k on the plate of V2B. I had 110k resistors rather than the 220k resistors between the mix wiper and the plates of V4. I'm also reading 280k on the two resistors on the plates of V4 that should be 470k. that's about all I could see that needs some work. I havent wired the LED yet because I want to get the faceplate on first so I don't have to disconnect the wires.

[sluckey]

I had a 680 ohm resistor rather than a 680k on the plate of V2B.

Uh, that resistor needs to be 68K. This is not causing your problems.

I had 110k resistors rather than the 220k resistors between the mix wiper and the plates of V4.

Nothing wrong here. That's exactly what you should measure if the MIX pot is max CCW. Those two 220K resistors are basically in parallel. To accurately check them you would have to unsolder and lift one leg.

I'm also reading 280k on the two resistors on the plates of V4 that should be 470k.

Nothing wrong here either. That's exactly what you should read when measuring in circuit. Those 470Ks and 100Ks form a series/parallel network. To accurately check them you would have to unsolder and lift one leg.

Have you verified all the board jumpers are in the correct positions???

[sluckey]

Verify the four underboard jumpers are securely in place. If you missed that long one you will have no guitar signal.

[Willabe]

Verify the four underboard jumpers are securely in place.

I only see 3 that you hi-lighted.

[sluckey]

The crooked one is actually 2 jumpers. Here's a better pic showing 3 of the jumpers. And the long one near the top of the board makes four.

[EKDENTON]

Yes i did the under wire connections the same way I ran them all the way through the turrets and bent them over so when i solderd components the wires will not drop out the bottom. I will try to get some hi res photos up soon but in the mean time i will keep checking, it's probably a wire in the wrong location. Thought it may be a missing ground but i sure dont see one yet......

[Willabe]

The crooked one is actually 2 jumpers.

Ok, I see it now.   

[uki]

Dunno if it is too late now, but it is better not to make underboard connections, I found it out the hard way(missed one and couldn't see it after the amp was all mounted and wired) now all my connections will be on top where they can be seen.

[EKDENTON]

So i unbolted the turret board and lifted it enough to get a mirror underneath so I could double check the underboard jumpers. They are in place as they should be. Here is a link to the high resolution photos. It is acting like an amp with a missing preamp ground. Bound to be a wiring mistake....just having trouble seeing it. This layout with double rows of resistors and wires under the board makes it hard for me follow the signal path. I traced the signal path as best as i could on the schematic. I did see one 100k resistor on the schematic that i could not find on the layout. All the parts are hooked up except for the LED.


http://s1266.photobucket.com/user/Ed_Denton/library/

[Willabe]

Looks real nice. 

But 1 of your power switch(?) lugs looks extremely close to a bolt just under it.

You might be over filtered in B+. A number of guys here like only a 10uF/8uF for the preamp input stage. Over filtering can change the preamp tone, make it thin sounding and/or have less chime and be less touch responsive.

You have 100uF/choke/100uF(?) then another 100uF and a last 100uF. The last 2 - 100uF's could be a 20uF or 10uF/8uF and the very last could be 10uF or 8uF. Or even just 1 - 10uF/8uF.     

[EKDENTON]

I saw that in the photo. It's actually about 1/4" away, for some reason it looks a lot closer in the photo.


On the caps I believe Doug's BOM is off the original Fender schematic which has two 100uf, one 47uf, and one 22uf. Your probably right it may be a bit of overkill. I went off Sluckey's design that has the two double 100uf cans. For fitting parts or buying can caps maybe he found it simpler to just do the two 100/100 cans. I don't know enough about reverbs to know if too much filtering would have a bad effect. Maybe it is different for reverbs than with amps? Since they are just there to smooth the dc ripple it seems like it wouldn't have any bad effect

[Willabe]

Since they are just there to smooth the dc ripple it seems like it wouldn't have any bad effect

Over filtering can change the preamp tone, make it thin sounding and/or have less chime and be less touch responsive.

[sluckey]

I did see one 100k resistor on the schematic that i could not find on the layout.

I count 7 100Ks on the schematic and I count 7 100Ks on the layout. Which one are you talking about?

Those 100µF caps ain't a problem in this unit. There are about a half dozen of these identical units out there (that I know of) and they all work very well.

I'll take a look at your pics and see if I can spot anything.

[Willabe]

Those 100µF caps ain't a problem in this unit. There are about a half dozen of these identical units out there (that I know of) and they all work very well.

I'm sure they will work great but they might sound a little different and have a different touch to them. 

[sluckey]

Your input jack is wired wrong. Fix that and see where you are.

I know you say your underboard jumpers are all OK. But I can't see any sign of a jumper on the turret I labeled as "A" on the attached pic. Please humor me. Check for zero ohms between turrets A and B. Then I'll shut up about it.

[sluckey]

Ed, I've looked over your board and it looks good to me. However, there are a couple resistors that I can't verify the value. Probably just my eyes and the angle of the pic. Anyhow, component values need to be verified.

I've attached a B&W pic of the board that can be printed and used to verify all component values. Use a highlighter to mark each verified component. I would verify resistors by color code AND an ohm meter. Just remember that some resistors may not measure accurately in circuit.

Oh, and one other thing... Remove the green wire from you EIC socket. It creates a ground loop that will likely cause hum issues. You can alternately leave the green wire in place, but use a cheap 2 prong to 3 prong "ground buster" AC adapter.

[EKDENTON]

Okay will do. Dang I had a feeling I wired the switch wrong ....since I usually make that mistake. I bet I looked at it more than anything else. Let me see what fixing that does.

I did check all the resistors and replaced the 680 ohm to the 68k. Theo other 4 that were reading off you mentioned should read off unless I unsoldered them for a reading.

I can't  tell what these little blue metal film resistors are by the color code. They all came mixed in one bag, I had to search one at a time by measuring them for the right resistor. The color bands all look black or brown to me. I saw one with a faint yellow tint....LOL. I like the tan color resistors better I can see what color the bands are.

[EKDENTON]

Fixed the jack before going to work. Now I have some guitar signal.  Plenty of hum. I disconnected the green wire on the power cord receptical. No change in hum. Signal is weak. Reverb controls seem to be working vibrato controls are not. Does the LED anode connect to the cathode of the 12ax7? It's not lighting ...thought I had it oriented correct.m

[sluckey]

Does the LED anode connect to the cathode of the 12ax7? It's not lighting

Yes. The LED will be flashing at the tremolo speed if the oscillator is working.

[sluckey]

All your voltages seem low to me. What voltages do you measure at cap A, B, and C? What voltage on V3 pin 8?

[EKDENTON]

Caps
A supply= 298vdc
B supply= 274vdc
C supply= 188vdc
V3 pin 8=26.52vdc
Secondary voltage at the transformer= 234vac
B+ node= 304vdc




Mojo 779 multi-tap transformer, i am using the black and white wires on the primary for 120vac line power. their is a 100vac tap that would raise the voltages. Our line voltages here are usually right at 120vac.




http://el34world.com/Transformers/files/MOJO779.pdf

[EKDENTON]

I just pulled out the 6K6 and took voltages at the same locations:


B+ node=324vdc


A supply=322vdc
B supply=295vdc
C supply=242vdc


Could this NOS 6K6 tube be bad?


With a 6v6 in:
B+313
A=308
B=295
C=194

[sluckey]

6V6 voltages look better. Node C is the only one that bothers me. Check that 10K on the cap can. Unsolder one lead if it doesn't check good in circuit.

[EKDENTON]

It's 10k.would the bleeder resistor cause the voltage to drop? I have it on the C node to ground 270k.

[sluckey]

What bleeder resistor? You don't need a bleeder in this little circuit. But that ain't dragging node C down.

There is a discrepancy between your tube voltages and the voltage drop across that 10K resistor. The currents should add up but they don't even come close. I'd like you to measure the voltage at node B and node C again. And also measure the voltages on all pins of V1 and V2 again. I want to make it all jive.

[EKDENTON]

Okay, will do. I don't get home until late but I will post it soon as I can

[EKDENTON]

Here are the voltages with using the 6v6 with all the tubes in.
V1
1. 148.5
2.-1.1
3. .745
4. 2.98
5. 2.98
6. 197
7. 0
8. 1.52
9. 2.98

V2
1. 103
2. 0
3. 1.31
4. 2.99
5. 2.99
6. 109
7. 0
8. 1.32
9. 2.99

B node 292
C node 199

[EKDENTON]

 C node  should be around 290v?


.029mA*10,000


The 6G15 has 12ax7, 6k6, and a 7025. Maybe this PT is too small for the extra two tubes?


I was also looking at the schematic and layout. They both show a 1 amp slow blow fuse. That may be a little small, I put in a 2 amp fuse. The filaments will draw around 1.5.