Radio Control Transmitter Help

[Gorilla]

Hi, I have an old Futaba Magnum Jr FP-t2pka radio transmitter for a radio control vehicle. I last used it about a year or so ago and stored it in a climate controlled area.
This year I went to use it and placed good working batteries in it and found it doesnt work. I checked the batteries with a Digital Multimeter and all batteries are good. I flicked the power switch again and the voltage meter needle doesnt move. I tried the batteries in another transmitter and it worked. I went back to the non working transmitter and took the case apart. Plug the batteries into the slot and checked to see if I had power where the red and black wires are connected to the contacts. I do have power there. But this is where I need someone with electronics knowledge to lend a hand to me to guide me on how to check other things with the DMM to find out what went wrong with it.

Here are some photos of what it looks like. Hope someone can help out.

 

[kellys_eye]

Looks like the power leads go via a charging socket(?) up to the main board. Check that the socket contacts haven't corroded or got dirty. Push a plug in/out of there a few times to 'clean it up'.

 

[Gorilla]

I believe it is a charging socket. It looks to like one. I dont have the manual any longer and havent searched online for one yet. I plan too.
Thanks I will try what you recommend and see what happens. I will post results as well.

 

[Gorilla]

The socket looks pretty clean. I did run a plug in & out of the jack and still no power. I checked the wire leads on the jack and it seems like I am getting power there.

 

[Gorilla]

Anyone?

 

[davenn]

Anyone?

well you have been away for a long time

did you ever find some circuit info online ?

have you followed the power wires up to the circuit board they go to ? is there power there ? is there a switch somewhere ?

you photos are a bit dark and small so it's difficult for us guys to see what goes where


Dave

 

[Gorilla]

Thanks Dave, Sorry for the dark pics. The only thing I was able to locate was the manual on it but its doesnt include any schematic on the boards or wiring. I did manage to get this straightened out last night and it was two bad batteries. For some reason they showed good voltage when I first checked them. I wasnt able to mess with this since i last posted and for giggles I retested each battery last night. Viola found the two culprits. Imagine that. All that wondering, thinking about it, posting, re-searching, and tearing it apart for a misreading on a couple batteries.... Sheesh... I guess like they say measure twice cut once. Although to my defense I did check the voltage twice on them before I posted a thread. I got 1.3v to 1.5v on 8 of the batteries. Now I get 1.5v on some while two showed .200 to .394. lol!

In regards to another question off this topic, you wouldnt know any good tutorials on learning how to build a guitar amplifier would you? This site seems pretty decent for electronics and Im itching to learn how to build a tube amp. I read about the book by Dave Hunter The Guitar Amp Handbook. Not sure if it would be of any help. I was wondering if it was a good start or not?

 

[davenn]

In regards to another question off this topic, you wouldnt know any good tutorials on learning how to build a guitar amplifier would you?

not offhand ... I would have to go googling myself to have a search around
you would have to decide on power level, whether you want portability as well ??

 

[Gorilla]

I wanted to clone the JTM 50 amp. I have a schematic for that. By portability do you mean a selection of power levels or just moving it around? If just power level then for me I would be happy on the 120vac U.S. standard power level.

 

[davenn]

I wanted to clone the JTM 50 amp

pretty sure that is a tube amp ...... do you have the expertise to build one of those ? high voltage experience etc ?

By portability do you mean a selection of power levels or just moving it around?

being battery powered

 

[Gorilla]

Yes sir, its a tube amp for sure. Im reading as much as i can find. Read that the Guitar Amp Handbook was a good start on how they work. Also reading and watching video tips by some of companies that offer dyi instructions on building the clone. I have a parts list gathered for the build. I just havent purchased anything yet. I do know enough to work one handed and also if I dont know something I know to research before I do any touch or probing. I gave another thought of buying all the parts and if I didnt feel comfortable with it I know a local guy that repairs them and thought maybe he could wire it all up for me for a last resort. I needed to check with him as well before I purchased any of the parts.
I have changed some components out of my old marshall amp some years ago and built a bleeder box to drain the caps. So I tinkered around with my own when I needed something changed,swapped, or replaced. I got a diagram from a guy over your side of the pond that played in a band called velatones. He sent me a info sheet on how to build it. Still have it today.

 

[kellys_eye]

Consider purchasing a simple non-working amp and doing a 'restoration' on it. If it comes 'complete' then fault-finding should be easy (most have readily accessible schematics and parts are still available off-the-shelf).

Purchasing the individual parts is more than often a lot more expensive than starting out with a complete unit!

 

[Gorilla]

Thanks kellys_eye. I appreciate the input and help. I do have a Epiphone Valve Jr amp that I want to mod. So I figured that would be a good start? I am researching how to read schematics and finding a few good you tube tutorials by a guy called Blueglow electronics. He makes some interesting videos on electronics esp. tube amps. I also found a book called building valve amplifiers and the guitar amp handbook that I planned on buying soon.
As for the complete JTM50 (original) prices have inclined on them. It is around $7k-$8k for one. The clones arent too far behind. Where as a kit by triode electronics comes in around $300-500. or so. I just cant afford an original and the clones are $3200+ So I felt a kit would be a good start to get me close to the tone I desire. I am wood work handy and can make my own box for the head.I know where to order the tolex for covering the box which is only about $35. Ive found a few members who were willing to help on how to bend up the chassis out of a metal sheet but they are only $80 for a pressed chassis already drilled with holes by a few companies. I will tinker with the Valve Jr head I have here before doing anything else though.