The Steel Guitar Forum

Hey guys, just doing some troubleshooting! Nash 112 will turn on but no sound. Speaker checks out! With pre side turned all the way off post side gets a small signal. Any ideas on what this may be amp guys? Also, can hear noise in pregain while turning knob but no sound.
Thanks, Shannon

Maybe try a jumper cable from preamp out to power amp in. Those jacks are notorious for issues. Sometimes just plugging in and out a few times will work.

If not the jacks, as above,

If you had a way to send your preamp out to another power amp to see if the signal loss was in the preamp -

and a way to send a preamp signal from another amp into the power amp input to see if the loss is in the output

At the very least you could diagnose whether the issue was upstream or downstream of this point, and then could have a proper discussion with Peavey Customer Service / Tech Support as they will know the most common failure points on either side.

Input jack solder and wiring also worth inspecting.

I found the nashville 112 schematic which shows a bunch of 4560 op amps then stops at the preamp out jack. The manual's signal flow chart has a block labeled: " 80 watt power amp" which I would bet money means maybe a separate power supply section and one lm3886 11 lead ic screwed into an aluminum heat sink. If you have signal on the pre-amp output jack and the speaker works, that amp is blown or something in the power supply isn't working. Sometimes the power supplies will be fused or have a protection relay but without that part of the schematic I just can't tell. 3886s are cheap as are most if not all of the supply parts. Other than gougers, Texas Instruments listed them for around three and a half bucks but were out of stock. If what was suggested doesn't work and a known good signal going into the power amp produces no sound, contact me and I can send you a replacement unused LM3886.

The Nashville112 does not use an LM3886, or it didn't use one last time I looked.

There are three potentials for no sound. The previously mentioned Preamp out/Power Amp In. Also the Pre Eq out/in loop and the Post Eq out/in loop. Try a guitar cord between the out and in of each one. One of these is the likely problem. Long shot for some other electronic problem.

How about it Shannon? Any luck in tracking down the loss of signal? Jerry, fair enough, but what is the 80 watt power amp module? Do you have a schematic for it? I haven't been able to find anything at all about it.

Ther power amp is a conventional amp, not a class D amp.

The LM part means linear monolithic and although I suppose you could run a pair in a Class B arrangement and could even amplify a pulse width modulated signal like Class D, most uses I have seen just use it as a straight bipolar supply amplifier which, as a zero signal would place it in the middle of it's characteristic curve, puts it in the Class A camp.
There are many variants including a dual in one package in that family. It was revolutionary at the time because I think 8 watts was the limit a one package audio ic was available in. National's 3886 Overture series peaked at 68 watts. Just imagine the savings in design and procurement for a solid state amp company when that came out. All this predates the class D in guitar amps who's main selling point is efficiency and light weight. They are popular but we'll see which amps are running 20 years from now. As Mr. Scott said: "The more complicated the plumbing, the easier it is to stop up the drain."

As Shannon seems to have gone missing I have no qualm from straying from the thread. My interest here is to find out about the mysterious Peavey Nashville 112 power amplifier module which, as this forum hosted a thread about that amp in 2007, and in all that time no schematic has surfaced leaves me mighty curious. I've never had one on my bench so to all those many who have had one and suffered a power amp failure; What is the power amp module?