Not tube related, but shooting in the dark...

[bradicusmaximus]

I tried to search and see if there was anything previous both here and on The Google, but I've had no luck, so I figured I'd pose a quick question or two:

A buddy of mine has a Gretsch 7154 Nashville amp he picked up. It's definitely cool and huge but trying to get some information on it is proving insanely challenging. It's working ok, but I'd love to locate a schematic on it that wouldn't cost me a significant portion of its purchase price. But failing that, I'd be fine just finding out what kind of pilot lamp this thing ran since that seems to be burned out.

Any help would be greatly appreciated.

Thanks!

[sluckey]

A good start would be to measure the voltage across the lamp socket. Look at the circuit and see if you can determine what it's connected to. Post a hi rez pic of the lamp.

This ebay item shows a partial schematic and has the lamp connected to 120VAC. So just find a 120vac bulb with the same base...

https://www.ebay.com/itm/Vintage-Gretsc ... 0677.m4598

[Stevem]

With a SS amp the pilot lamp could get its voltage feed from the AC side of the supply and would likley be a 120 volt lamp , or on the D.C. Side of the supply.

Since this amp is rated at 75 watts I will take a guess that the D.C side of the power supply is atleast 40 volts, now if D.C. supply is a duel rail type the the lamp could be powered off the full 40 volts or so, or the positive or negative 20 volts or so that makes up the full 40 volt supply.
When a lamp is on the D.C. Side of the supply and you play the amp loud, when the power supply dips down, so will the Briteness of the lamp.

So in short, yes measure the voltage on the lamp socket be it AC or D.C.!

[bradicusmaximus]

A good start would be to measure the voltage across the lamp socket. Look at the circuit and see if you can determine what it's connected to. Post a hi rez pic of the lamp.

This ebay item shows a partial schematic and has the lamp connected to 120VAC. So just find a 120vac bulb with the same base...

https://www.ebay.com/itm/Vintage-Gretsc ... 0677.m4598

Thanks for the link - I did not come across it in my searches, but that picture of the schematic was incredibly helpful.

[sluckey]

I'm a bit suspicious of that schematic. It clearly shows the lamp bulb connected across the 117VAC mains. But the lamp bulb is labeled 356, and a 356 bulb is a 28v bulb. I'd love to see a pic of that bulb showing any writing on it.

[tubeswell]

In the wiring position on that schematic, it would have to be a mains-voltage lamp. But as Steve says, it could be the wrong schematic...

[bradicusmaximus]

For those asking, here's a picture of the bulb in question. There are no destinations on it - at least that have survived almost 50 years, but the base is stamped "westinghouse".

32253624_10212189188188166_913444805470584832_n.jpg

[martin manning]

Trace the circuit and/or measure the voltage on the socket. What is the diameter of the screw base? If it is 12mm, it would seem to be a 3S6 bulb (as noted on the linked schematic), which is 120V. You can probably find that at a hardware store or Home Depot.

[sluckey]

Ah, I see Martin was quicker on the draw...

Yes, measure the diameter of the base. I'm guessing about 12mm (7/16"). If so, that's an E12 candelabra base. You may just have one in a night light around your house. Or on an antique Christmas light string. If no luck there, try Walmart, or look in the dusty bins at an ACE Hardware, or better yet, a mom and pop hardware store. Still no luck, then go to this webpage and select one of the 3S6 130v bulbs...

http://www.bulbtown.com/SearchResults.asp?Search=3S6

[martin manning]

BTW, the complete schematic for this amp is included in Jack Darr's Electric Guitar Amplifier Handbook, pp 354-355, but the transistor part numbers are not given :^\