Reverb troubleshooting checklist

[davidwpack]

Ello! I built the "add reverb to the western electric circuit" and it's not reverbing. Otherwise the amp sounds fantastic but no reverbs. Here's what I've checked: continuity of RCA cables=good. Voltages look good. I substituted tubes in V1 and V2, including putting a 12 AT7 in V2. I plugged the reverb output directly into a speaker and got sound. My jack wiring appears to be correct. No crash in the "crash test". I visually checked the tank and everything appears to be intact. Also it's a never-been-used tank. It seems like the tank is at fault but I'm not sure. Any ideas of what else to check? Please? Thanks!..dave

[punkykatt]

with your ohm meter check the rca jacks on the tank. you should get a reading  on both jacks.

[SILVERGUN]

Make sure that you remove the packing foam from underneath the coil springs.
Ask me how I know.

[Colas LeGrippa]

LOL !

[davidwpack]

Resistance readings are: 1.7 ohms input and 216 on the output. Yeah, I removed the foam. There's one really thin piece glued down but it's not touching or otherwise interfering with the springs at all. So wiring or switch problem then?

[sluckey]

What amp circuit did you put this in? Got a schematic of exactly how you wired it?

Sounds like your driver is correct but the recovery is not. That means V2B circuit if you followed Hoffman's drawing. Very straightforward recovery. Check for wiring errors. Measure voltages on V2 pins 6, 7, 8. Be sure both V2 filaments are lit up.

[davidwpack]

Hey, yeah this is precisely like Doug's drawing with no deviation. Here's my readings: V2-1=470 v, pin 2=0.0, pin3=6.68, pin6=67.0, pin7=0.0, pin8=.92
Heaters are 3.2 to ground and 6.3 across.

[davidwpack]

Also this is with the 12AT7 still in place.

[sluckey]

Voltages for pin 6 is low. According to my math, the B+ node that pin 6 100K plate load resistor is connected to is only 179v. Is that correct?

Put a 12AX7 in V2 socket and recheck voltages.

[davidwpack]

12AX7 readings: pin 1= 472, pin 2=0.0, pin3=3.22, pin 6=100.1, pin7=0.0, pin8=.72
Voltage at node =187

[sluckey]

Voltages look OK. I'd guess you have a wiring error between the tank and V2b recovery tube or between V2b and the MIX pot. Or a defective tank.

[davidwpack]

I don't know. I just went over it several more times. Did a continuity check between pin 7 and reverb input, and between input and footswitch Jack's and everything seems to check out. Maybe it is the tank. Know of any other tests besides checking the ohmage? It checked out when I measured the tank input and output. Guess maybe I'll order another tank and find out. Thanks. I'll post back if I can figure it out.

[davidwpack]

Stupid question: there is no difference between "reverb" cable and standard RCA cable is there?

[sluckey]

Cables are the same. Just a shielded cable. Try this... Unplug the cables at the tank but leave them connected to the amp. Now touch the tip of the cable that connects to your recovery tube V2b. You should get a loud buzz just like you get when you touch the tip of a guitar cable that's plugged into the amp. Do you?

[davidwpack]

No. Not any noise at all.

[VMS]

Can you post a picture, maybe there is something wired wrong

[davidwpack]

A couple Pictures.

[VMS]

I can't see from the pictures but what wire goes to pin7 on your reverb tube?

and what is that rca jack where hot is connected to ground?

[2deaf]

It looks like the hot on your return jack is shorted to ground by a little wire.  It also looks like the 220K on the return jack goes to the hot on the footswitch jack.  What is the resistance between the tip of the cable that sluckey had you touch and ground?

[sluckey]

No. Not any noise at all.

Fix the jack wiring and it will probably work.

[davidwpack]

I've got 1.5 ohms resistance on the cable. I desoldered the ground from the return jack and the amp sounded completely awful but there was reverb. I'm on the right track I'm just trying to translate Fender drawings of reverb jack connections to what they actually look like.

[2deaf]

As a quick test, short the footswitch jack and see what happens.

[sluckey]

The FS jack tip connects to the reverb input jack tip. and a wire connects the reverb input jack tip to V2 pin 7. The 220K resistor connects between the reverb input jack tip and the ground lug for the reverb input jack.

[davidwpack]

Ok I just shorted it and nothing happens. I found this picture in an old post and it looks like the way I have mine wired assuming #1 is the output, #2 is the footswitch, and #3 is the return. I think #4 is for vibrato or something. I think this is Sluckey.s picture.

[davidwpack]

Oh I was typing this while you replied. I'll check it out. Thanks!

[davidwpack]

Ok. I believe I've got the resistor in the wrong place. I'm getting ready to start another 24 hour shift at work. I'll change this around Friday morning and report back. Thanks for everyone's help!

[davidwpack]

Reverb is reverbing! This amp is a rebuild of my first amp and was always my platform for experiments. That's why I decided to add reverb to this one. It's pretty poorly laid out and I'm getting a lot of noise. Hum and buzz which I've reduced to the OT wires being too close to the reverb circuit. There's also a high pitched microphonic sound which increases by increasing the mix pot. I'm getting ready to reroute the OT wires which I'm sure will alleviate the hum and buzz. I'm not sure yet if it's attributing to the microphonics yet though. Find out shortly. Thankee..dave

[davidwpack]

Success!!... almost. After a long and arduous poking, prodding, desoldering, moving, and resoldering, it's now noiseless, loud and has really nice, lush reverb. This happened after unplugging the foot switch with the reverbs engaged. Now, no noise, hum, or anything. I figured a defective foot switch but it I plugged it into my VibroChamp and it switches it without introducing any noise. Are vibrato and reverb switches different? Anyways, many thanks to all of you for yer help!!!!!!!!...dave

[sluckey]

Are vibrato and reverb switches different?

Any simple footswitch will work for tremolo/vibrato, but your reverb circuit must have a shielded cable between the amp and the footswitch. The very low level reverb signal runs all the way out to the footswitch and is very susceptible to picking up noise if you don't use a shielded cable. Just think of it as a guitar cable. Any shielded cable will do the job, even a guitar cable. The center of the cable connects to the center pin of your RCA plug and the braided shield connects to the shell (ground) of the RCA plug.

[davidwpack]

Ok. Gotcha. I'll probably just build one then. Thank you very much!