So am I looking for a transformer that has " dual secondaries " ?  

"18Vx2" does the x2 mean dual secondaries ?

Does "18Vx2" mean the same thing as : 18-0-18 ?

Is there a way for me to determine the wattage or amperage requirements ?

Sorry about so many questions on this.  My concern is that I want to hook it up right the first time.  I don't have any replacement channels for parts so if I fry it I'll just have to gut the cabinet.  I also have to order over the internet because I don't have any supply channels around here for this kind of stuff.

This picture should help clear things up a bit.  Thanks for your help.  I just need to get a 2X18 DC transformer right?  What numbers am I looking for in watts and amperage?  I can't find any information about the current transformer.

I think I'll get an IEC 14 connector and mount it on the chassis somewhere close to the power supply.  Should I runt the ground wire to an area in the chassis next to the power transformer?

What's the best way to cut a hole for the IEC connector in this type of chassis?

Can anyone suggest a power transformer that would work for this amplifier?  120V - > 18V (2X what does this mean ?).  I see some 18V transformers that don't say anything about 2X 18V sceondary.  Would I need 2 of those to make this work?

Thanks

I picked up this amp about a year ago and I need some advice on how to convert it from 220 to 120.  I live in United States and my wall current is 118V AC.  Please see attached pictures for more information.

I'm assuming I need to :

- get a transformer 120V AC to 18V DC output.
- change the power connectors(can I user the same mains wire?)
- switch issue(can I use the same on/off switch?)
- change the fuse specifications(what type of fuse do I need?)

Quote from: phatt on January 27, 2010, 09:36:00 PM
Hello Zappacat,
There is no magic size it's not the space shuttle the word you need to concentrate on is *ABOUT* this wide *About* this deep.

You only need to look at the massive variations in what has gone before.

Guitar speakers are low compliance drivers and as such do not depend on box size.
If this where not so then every open back guitar amp combo on the planet would sound horrorbillus.

Close the back of the cab and the sound will tighten and focus a little more.

So moving the front panel in by 3/4 inch will not effect the sound.

Speaker cloth should not lay flat on the baffle board,, you need to raise it slightly off the board as the cloth will flap againt the board.
You need to put a small moulding all the way round the front outer edge.
see drawing.

Cheers, Phil.

I'm confused, many of the guitar amp speaker enclosures I see on the web say not to alter or scale the dimensions due to the fact they've run it through some sonic simulation software during the design process and determined what the dimensions should optimally be.  Even down to the point of making internal bracing schemes exactly to their specs so not to interfere with the internal volume(in terms of space) in the enclosure.

Also, the AX84 speaker planshttp://ax84.com/static/corecabinets/AX84_1x12_Cab_09.08.03.pdf even instructs you to drill different size ports in the back of the speaker cabinet based on what tuning you generally use.

Can anyone enlighten me on this?

What's a good simple speaker enclosure to build just for someone starting out?  I'd like to be able to experiment with it open vs. closed back.  I don't want it to be heavy but If it's better for the sound to use more dense wood then I could deal with that.

Thanks in advance.

Can you guys tell me what basic parts I need to construct a 9 volt DC 500mA power supply?  I live in United States and my home socket voltage is : 118 volts AC.  

I see after reading about wall warts / AC adapters on Google that some are straight AC, some are rectified AC, some are rectified and smoothed AC.  Any way to tell by the picture which category this adapter falls into?  After messing around with some more complicated audio projects and not getting acceptable results I'm beginning to realize how much I don't know about electronics.  I thought I'd give this project a try because it should be simple, right?

I attached a picture of the transformer back label for all the technical specs I have.  This power supply powers a Studiologic keyboard controllerhttp://www.studiologic.net/sl-990xp.html.  Thanks

It's beautiful.  I had a similar Peavey amp when I was in junior-high / high school.  Approximately 1979 - 1981.  I bought it brand new and only had it for a couple of weeks.  Someone stole it from me at midwestern music camp in that same time frame.  It was locked up in a shared storage room with some other peoples instruments.  One day I went down to get my amp and guitar(it was a gibson THE PAUL) and there were people standing outside the storage room with police.  Someone had gone in and taken everything in the room.  Most of what was taken were reed instruments.  The reed instruments were found later in a dumpster on the other side of town.  My Gibson THE PAUL and Peavey amp were never seen again.

Ironically, one of the cases containing a guys clarinet kit was valued at $15,000 in 1980 !!!  All of the other stuff was valued from $2000 to $5000 all found in the dumpster.

I miss that amplifier but as the years have passed I can't remember exactly which one it was.  Are there any sites with historical pictures of Peavey amps from this era?

I've got some old televisions I've been cannibalizing for parts.  Unfortunately, ALL of them are solid state and from the late 90's early 2000 era.  Most of the transformers and power sections seem to be built into a larger circuit board making it difficult to extract transformer without damaging it.  Are any of these parts worth keeping (for audio projects like discussed in the forums here) besides the heatsinks or am I just creating a huge pile of crap to clutter up space and make more of a mess?

Thanks guys.  With your help I fixed this.  The solder point going from the fuse to blue primary wire had disintegrated.  There was just a hole left there.

I can't remember which speaker lead went to what post on the speaker connections.  Does it matter?  There's a blue and white wire coming from the amp chassis for the speaker connections.  One of the speaker terminals have a red dot on it.  Any clues as to which wire goes where?

I've got 120 volts all the way to the fuse.  

What are the two blue components in the pic behind the fuse?  I'm thinking there should be continuity between the first one and the trailing fuse lead but there is none.

So the black wire coming into the wall turns into yellow after the power switch.  I'm getting 120V all the way through the heat sensor and the fuse.  What should the white wire(I have three wires from mains black, white, green) be reading for voltage ?

Quote from: J M Fahey on March 23, 2010, 10:36:10 AM
1) AMP UNPLUGGED !!!!
Measure resistance from Black to Blue, post result.
2) Multimeter on "beep" position, short probes to check they beep, then one probe on black wire, other to power plug, one blade should beep. Mark it somehow (tape/marker/nail paint).
3) repeat with one probe always on blue wire; trace back the connection until you get to the other, unmarked blade; that's to say, touch in order:
both pins of power switch , one should always beep, the other follow on/off switching;then leave it on, proceed to thermal switch mounted on heat sink, both pins should beep; then touch both pins of fuse holder, both should beep; then touch the unmarker power plug blade, it should beep; finally apply one probe to each power plug blade, it may not beep (depends on your multimeter) but it must show continuity.
4) Wherever the beep stops along the way, that's where you lose power.
5) It all depends on first having continuity across black/blue wires, otherwise we are wasting time.

1) 9.6 ohms
2) done
3) neither pin of power switch yields continuity with blue primary transformer wire
4) still working on this
5) Do the black/blue primary transformer wires need to be disconnected(desoldered in this case) from the circuit to test continuity, resistance, etc...?

I'm getting 1.8 volts AC on EACH of the primary wires going to the transformer which are blue and black.  Maybe I'm not measuring the voltage properly.  With the power on I put one probe on either the blue or black wire going to the primary but where should I have the other probe?  Should it be connected to the main chassis ground or somewhere else?

Quote from: J M Fahey on March 22, 2010, 05:24:03 PM
1) Amp unplugged. Turn it on, grab the power cord, measure resistance across ths hot and neutral power plug pins. Do you have continuity?
2) Plugged amp, power on. What AC voltage do you measure from secondary center tap (R/Y) to each Red wire?
3) What DC voltage do you measure across C48 and C49?

1) No continuity with respect to question 1.
2) I'm getting 0.00 AC voltage for both secondary center taps (should this be +- 36 volts?).   
3) I'm still trying to figure this out.

Thanks

Attached are the schematics for the Peavey Studio Pro 40 / StudioPro 40 combo amplifier.

I'm trying to fix a friends Peavey Studio Pro 40.  It shows no signs of life when plugged in.  I pulled out the chassis and checked the fuse (is there only one?) and voltage levels coming into the amp.  Those were OK.  Now I'm looking at the power transformer.  The numbers on the transformer are 705-18712 .  A google search on this number yields nothing.  Am I looking in the right direction to start at the PT transformer from this point.  Is it safe to check power transformer voltages without a load on them?

Peavey parts no longer carries the transformer but a substitute transformer number of 705-18762 was given to me at a price of $ 42.99.  Google search for 705-18762 part number yields nothing.  If the problem turns out to be the transformer can I get something that will do the job elsewhere for less ?  Can anyone tell me transformer specific requirements based on the schematics I posted in the schematics section.  It may sound like I'm cheap but the guy I'm trying to fix this for is even more broke than I am right now and I can't have this situation end up COSTING me money like these things sometimes do.

Thanks in advance.