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March 28, 2024, 04:38:08 PM

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#21
Amplifier Discussion / Re: Acoustic 134 reverb
Last post by g1 - March 22, 2024, 11:58:15 AM
Service manual attached.
This one is solid state so I don't think either of those tanks would be correct, but it is possible.
Reverb circuit shown on pdf pg.17
Drive is taken through cap C205 from a 40408 transistor.  Return into a MPSA05.
#22
Amplifier Discussion / Re: Acoustic 134 reverb
Last post by Loudthud - March 22, 2024, 12:51:24 AM
The Acoustic tube amps probably use the same tank as the tube Fender amps with an 8 or 10 Ohm input impedance.

Check the 230 or 330 amp schematics to see if the drive circuit is similar to the 134. That would indicate that the 1BB1D1B is the correct tank.
#23
Amplifier Discussion / Re: Acoustic 134 reverb
Last post by Tassieviking - March 21, 2024, 07:45:28 PM
I sometimes look up tanks at https://www.amprepairparts.com/reverb.htm if I don't know the right part for an amp.
They only mention 2 different tanks for any Acoustic amps, the 8BB2D1B tank as an Upgrade for the 1BB1D1B reverb tanks used in Acousticâ„¢ amplifiers from the 1970s, such as the  models 230 and 330.
The other one is a  8AB2D1B Also used in the Acousticâ„¢ G60T (Model 162 or Model 163).

Personally I have no idea what went into those amps, but since you most likely have to drill new holes to mount it I would go with a large 3 spring tank myself.
#24
Amplifier Discussion / Re: Question about Marshall mo...
Last post by Dude Manhoney - March 21, 2024, 02:20:12 AM
I got this amp from a friend of mine He just asked me one day when I was doing some work at his house if I wanted it and he gave me it and the Big M cabinet that he bought with it back in 1973 or 74 The cabinet has AlNico magnet rolla speakers it was not functional, he said the last time it was plugged in smoke came out well I replaced all the caps inside of the amp (all leaking) and the dry rotted power cord and when I fired it up it sounds pretty dang good and when you add a little EQ pedal to it it's even better has a lot of good tones to it. I wasn't sure about the slave output but I saw on the board where it says mixer out.

I wasn't sure about turning the cab ohm selector switch to off (but why would they have it if you couldn't use it right)

I wasn't sure about this I didn't know you could run solid state amps without a speaker so that's good to know thank you so much for the info.
#25
Amplifier Discussion / Re: Question about Marshall mo...
Last post by Tassieviking - March 21, 2024, 01:58:26 AM
The slave/direct inject is a signal out for a separate power amp or mixer, you can use this to go to another amps return socket.
The effects send and return plug is a single stereo socket, you need to use a "Y"splitter cable to use this.
Stereo plug to 2 mono sockets.

The slave/monitor is the same signal as the send part in the effects output.

The stereo plug will have send on the tip or ring and return on the other tip or ring, I am not sure which way around it is.

The 2098 was the head version and the 2200 was the combo version of that amp.

You can turn the speaker selector to off, or just leave the speaker disconnected as far as I know, its a solid state amp so it should be no problems.

#26
Amplifier Discussion / Question about Marshall model ...
Last post by Dude Manhoney - March 21, 2024, 12:59:40 AM
I've had no luck trying to find a owner's manual... My question is on the back of the amp there is this slave \ direct INJN and the output ohm selector switch has an off position, also on the main board where the wire comes from the slave connection to the board the board says "mixer out"...
So the question is can I turn the output selection to off and use the slave connection to go into another amp or mixer without having to connect a cabinet?

I was even thinking possibly using it as a preamp before another tube amp just to see what it would do.

I added the send and return jack picture just show that the other is not an input or part of the sending return.

Couldn't figure out how to add pictures to my post so I gave the link to where I asked the same question in Marshall forum so if you wanted to see the pictures you can look there thanks in advance.

I posted this same thing in Marshall forum but I get no answers I couldn't figure out how to post pictures here
#27
Amplifier Discussion / Re: Watts vs Volume (db)
Last post by g1 - March 20, 2024, 08:39:30 PM
Quote from: JonnyDeth on March 20, 2024, 02:56:58 PMWell, looks like I wasted all that time going to college for electrical engineering, thanks for the clarification  ::)
If you can't apply it, I guess you did.
Amplifiers are rated into resistive loads to take reactive power out of the equation. 
Note that I specified amplifiers in my earlier comment to exclude what you said about speakers.

When one walks into a new room, it's best not to have the flamethrower on and start out with the idea that everyone else has it wrong.
#28
Amplifier Discussion / Re: Watts vs Volume (db)
Last post by Loudthud - March 20, 2024, 07:27:43 PM
What is VAR and what does it have to do with anything ?
#29
Amplifier Discussion / Acoustic 134 reverb
Last post by Pete - March 20, 2024, 04:01:33 PM
I'm repairing / refurbishing a 1970s Acoustic 134 guitar amp. It's missing the spring reverb tank (someone obviously removed it some time in the past) and I'd like to install a new one but I'm at a loss as to what the proper specs are or how to find them.

The service manual/schematic does not provide any specs; the only information listed there is Acoustic part # 315006 (which has proved useless so far). I have contacted several online companies that deal with vintage equipment and/or reverb tanks (Studio Sound Electronics, Accutronics, Model Electronics, Tubesandmore, Ruby Reverb, etc.) and no one has been able to find specs or suggest a proper replacement.

There are 4 mounting holes in the head chassis for the tank - long dimension between holes is 222mm (8-3/4"), short dimension between holes is 99 mm (3-7/8"). I'm told this makes it an "8 series tank", but that just indicates the physical size. Need to know input and output impedance and grounding arrangements.

Anyone have a suggestion? I guess ideally I would need someone with a 134 to take a look at the reverb tank and see if there's any numbers on it. Or, tell me (1) what is the DC resistance reading across the input and output jacks? and (2) is the outside ring of the RCA jack tied to the reverb case on both input and output jacks? With that info I could probably identify a compatible replacement. Thanks for any help.
#30
Preamps and Effects / Re: Tube effects loop out int...
Last post by Tassieviking - March 20, 2024, 03:06:41 PM
I'm not 100% sold on the idea, the effects send signal can be too much to plug into the guitar input. If you keep the level down in the Orange it should be ok maybe.
If your Roland Cube has an auxiliary input then that should be able to handle it ok
If you have 2 inputs the normal one can handle 56mV and the overdrive one can handle 10mV so use the normal one if you do try the guitar in socket.