New "old" amp day and a question or two

JohnQ

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Hi all, I just picked up this old amp this morning and thought I'd ask about it here.

It's marked Tempo on the grill cloth but I can't find any other markings. I believe the model number for it is BB-65 and has a 12" speaker. Has pots for volume, treble, bass, tremelo speed and tremelo depth. Has three inputs marked "instrument" and one input marked "tremelo footswitch"

It has the following tubes in it- 12AX7 6AV6 6AQ5
The rectifier is solid state.

I plugged it in and it has a bit of a hum. I did not plug my guitar into it because it has a two prong plug and I've read that it should be changed out for a grounded plug. I believe the hum is probably caused by a wire that has become dislocated from the volume pot. There are two wires running in to the volume pot and the one that is broken is running to the treble pot.

Can anyone shed some light on this amp and confirm for me that the plug should be switched out for a grounded plug?

The wiring from power wiring is set up like so-

Power Cord wired to switch and fuse.
Transformer wired to switch and fuse.
amplifier006.jpg

amplifier003.jpg
 

KSG_Standard

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It should say made in Japan somewhere on it, those amps from the late 60s - early
70s...It's very low power, less than 5w...I can't tell you about the power cord, but there are some very knowledgable amp guys on here, someone will know details about this amp...
 

JohnQ

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It should say made in Japan somewhere on it, those amps from the late 60s - early
70s...It's very low power, less than 5w...I can't tell you about the power cord, but there are some very knowledgable amp guys on here, someone will know details about this amp...
Thanks-
I'm looking around for the markings, just can't find them. I'm thinking the label was on the back cover which is missing.
Pretty certain that two prong cord has to go, not plugging into it until I get it grounded.
 

SatelliteAmps

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Yes it should be switched out for a three prong plug. The third prong goes to a chassis ground.

Tempo is a made in Japan amp. Worth about $100-$150. Great value, decent sound.
 

JohnQ

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Yes it should be switched out for a three prong plug. The third prong goes to a chassis ground.

Tempo is a made in Japan amp. Worth about $100-$150. Great value, decent sound.

Thanks Adam! Do you know where I can find more info, like a schematic? I've searched for hours and can't find anything.

Also, it has an input for a footswitch for the tremelo, would any footswitch be compatible?
 

Rich

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Never heard of it.

While it's definitely a good idea to get a three-prong grounded cord installed, there's no reason why you can't plug a guitar into the amp as it is. People were playing through amps without ground plugs for decades before grounded plugs - and outlets - appeared.

I haven't got around to changing out the cord on my '66 Fender Champ and have no issues with it. The most common problem with amps that aren't grounded is when playing with a band - if your mouth touches a microphone or you touch the strings of another player's guitar or bass, you're going to get a shock. I used to play through an old silverface Bassman a long time ago in this one band I was in and was *very* conscious and mindful about not bearing down on my mic.
 

SatelliteAmps

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The problem with running an amp that is on a two prong cord is that there is potential for the chassis to become hot (live). If a person were to reach down and touch it, they could create a path to ground and shock themselves.

The basic idea for converting is just to put the green wire to ground, the black wire to the switch and fuse, white wire to the transformer side.

Here's a link with instructions (not written by me, but a good general guide)

Three-prong plug safety mod
 

JohnQ

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The problem with running an amp that is on a two prong cord is that there is potential for the chassis to become hot (live). If a person were to reach down and touch it, they could create a path to ground and shock themselves.

The basic idea for converting is just to put the green wire to ground, the black wire to the switch and fuse, white wire to the transformer side.

Here's a link with instructions (not written by me, but a good general guide)

Three-prong plug safety mod

Thanks, Adam. I wired up the three prong cord yesterday and it powers on but there is no sound. The vacuum tubes glow very dimly, so I think that may be the problem. Going to try and replace them today if I can find some locally. Fortunately, chances for finding them are good since we have a couple of old TV repair stores still downtown.
 

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