The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Anyone know where I can get a schematic for the Melaka. The radio receives fine but no transmitt I replaced the final and the driver but it's still the same.

hi there,,the pc board used in the melanka is the same pc board used in the galaxy 33 hml mobile unit...ept-360014b,,so go to cb tricks,then go to galaxy,,then to 33 hml...it will be the same radio,just in a base radio case.i would be looking in the area of the regulator..2sb754,,or in some cases they use a 2sa1012..good luck with your radio,,if you need any futher help.check with rick,he is the best troubleshooter on cbs i know....take care..........................ramblingman

thanks ramblingman and I agree Rick is a good guy and all kinds of help

ramblingman you were right on the 2sa1012 is bad Ill get a replacement monday Thanks again for the help.

hey there,,,if i were you if i could get one..id replace the 2sa1012 with a 2sb754 which is a 60 watt or a 2sb817 which is a 100 watt device..it will be more stable and run cooler too............................ramblingman

good idea ramblingman Thanks I think Ill do that

Well I replaced TR-51 and the Final and the Driver but still no transmitt. Is there something that could have gone short when TR-51 went out.

I can take a short pice of wire and touch the base and collector of each the driver and then the final. Doing this with another radio tuned to the same channel and close by.Watching the receive meter.The driver acts as it should the base seems to emmit a little less RF than the collector which I belive is correct. The final on the other hand emmits less RF at the collector and more RF at the base.Can someone please tell me if this is correct. I have little in test equipment so ill do this like a cave man.Anyone ?

when you key the radio does the on the air light up,and do you hear the light pop of the key or not..

I do not like to but in on other posts. However, this may help.

If original TR51 had gone short circuit, in some cases it also takes out TR50 as will.

What is the voltage at the collector TR51 in TX on AM and FM, and what is the Base and Collector voltage of TR45, TR44 and TR45. Let us know how you get on.

Yes ramblingman the ON THE AIR lights up and you can hear the switch from RX to TX.
And Rick I don't think anyone thinks your butting in.I think everyone here should apericate the help you give. I know I do.
Anyhow the Voltages are like so.
TR-51 Collector at transmitt AM= 3.51, FM=3.50
TR-45 Base at TX=1.35 Collector at TX=5.77
TR-45 Base at RX=minus 0.00 Cololector at RX= minus 0.00
TR-44 Base at TX=.54 Collector at TX=3.22
TR-44 Base at RX=0.00 Collector at RX=3.60
TR-43 Base at TX=.48 Collector at TX=3.50
TR-43 Base at RX=0.00 Collector at RX=3.60

Thanks Guys !

You appear to not have the volts to turn on TR44 and TR43. Can you adjust VR13 for 5.6 volts at the collector of TR51 after doing so recheck the voltages in my first post. Let us know how you get on.

Rick

I work out of town but when I get back at the end of the week Ill be sure to follow up.

Thanks Rick

sounds like it is probably tr-45 o/c,,from the voltage readings.tr-45 is the pre-driver.

ramblingman I replaced TR-45 earlier

Rick
I turned up 13 and now have 5.60 volts at TR-51 under TX AM and FM
TR- 45 TX is C=5.59V and B=1.14V
TR-44 TX is C=5.30V and B=.59V
TR-43 TX is C=5.60V and B=.52V

no transmitt

looking to hear back and Thanks!

Can you check the voltage on Pin 5 of IC9 and the voltage at each side of R233 and TR46 base, collector, and emitter in TX mode.

Rick

Pin 5 of IC-9 8.21Volts
Each side of R233 .01Volts
TR-46 at TX B=1.49 C6.05 E.75

When you replaced TR45 did you get the same transistor (2SC2538)?
It sound like you have TR45 in the wrong way round. If you have replaced it with a 2SC1973 or 2SC2076, look at them from the front they are E, C, B and 2SC2538 is B, C, E.

I replaced TR-45 with a NTE293 didn't have a replacement. TR-45 was a 2sc1973 I now have a new 2sc1973 I can install.
Also R223 has 0.00volts each side.

Are you sure that R223 has 0.0 vdc in TX? check R226 and R221 each side in TX mode. If you do not have any volts at the resistors then that the fault, check for broken track and cold solder joints.

Sorry Rick R223 has 8.92 and 6.38 volts I miss understood. Tr45 should be correct emitter is connected to R220

I touched up a few solder joints around the driver and final I now have about .5 watts on my RF meter.
TR44 RX B=0.00 C=5.97
TR44 TX B =.66 C =3.77

TR43 RX B=0.00 C=6.00
TR43 TX B=.45 C=1.38

Rick I realy appericate your help with this

Try adjusting VR13 for 5.6 at the collector of TR51, I know you have reset VR13 once but if you only have low voltage at collector TR44 and 43 and have 5.6 at TR51 you must have a bad track or bad solder joint from TR51 to the driver and final, or do you have a bad power supply.

Rick I did reset the collector v at TR 51 I dont think the power is bad. I will look close at other joints and the pc board.
Thanks again Rick

You should have the same voltage at the collector for TR44 and TR43 as you have at the collector TR51, as the collector is connected to TR43 var L34 and TR44 var L37.

I found out my V meter battery was weak. my V is the same now.i just dont have but .5 watts? you were right on about the power its running up to 16 volts at TR-51

You have lost me, what is at 16 volts?
Now you have a new batter in voltmeter, what is the voltage at TR43, TR44, TR45 and TR46.

Rick
I was speeking of TR-51 the power seems high to me but I dont know.
TR-51 at TX E=15.85 C=8.68 B=15.12
TR-46 at TX E=.85 C=5.90 B= 1.48
TR-45 at TX E.84 C=8.48 B=1.43
TR-44 at TX C=5.59 B=.63
TR-43 at TX C=5.52 B.55

So what is you power supply voltage?

power supply 16.12 volts

Rick I made a mistake the Volts I gave you for TR-51 were reading I wrote down and were taken from TR-41
TR-51 E=16.03 C=5.60 B=15.42

You power supply should be a max of 13.8 VDC. I think you need try a different power supply which is known to be OK or car battery.

I found a pot for the supply and set it to 13.87 volts. Close enough ?

Half a Watt?

Time to take loose the base and emitter legs of the final transistor and see if it passes a diode test across those two.

You can leave the emitter soldered to ground and do this with only the base leg unsoldered from the pc board.

Sounds kinda like an open base to emitter junction.

Or numerous adjustments out of whack?

Do you know any history with this radio?

Has it been like this since you first saw it? Or was it running okay and then just quit?

Gotta find that link to 'testing transistors with a meter'.

73

I have a Transistor Checker and the Driver and Final Check OK. I dont know anything about the Radio. The guy I bought it from said the Final went out. As it turned out it was TR-51 that was bad. Seems someone had the Power supply turned up.Everything Iv'e went through is in my post.Im not much of a teck as you can tell. Rick has been a great help and continues to do so. THANKS for RICK.
And thanks for your input. nomadradio

You may have a current problem with the power supply, can try a different supply just to verifier this is not the problem?

One think, which is not making much sense, is the collector of TR51 (5.60vdc) should be the same voltage as the Collector of TR44 and TR43 in TX. Do a visual for the collector of TR51 to the collectors TR43 and TR44 looking for a bad track or bed solder joint.

For you PM it looks like you have a bad final TR43, I think it would be best to change to see what the out come is.

Thanks Rick
Ill see if I can locate a new final tomorrow and Ill be sure to check the board.

Thanks again.

I think you try a different supply just to verifier this is not the problem?

Im not realy sure just how to do that.The radio doesnt have a plug to the rear for mobile use.I have a hot and ground on the board I can tap into but there are other wires coming off the supply that go to the front of the radio .Not sure what these are.

I dont understand I have traced the power up to L-34. On the power side of L-34 Volts stay the same at TX. On the side of L-34 close to TR-43 it drops.

Thanks again Rick.

I know you must have better things to do than fool with this.

Sounds like a nightmare but it look like you have the right guy helping you.

No doubt about it.

So everyone will know. The problem with the Melaka turned out to be a bad Driver. This was a new Driver and checks OK on ny transistor checker??? Oh well live and learn. I just wanted to thank everyone for there help. And Rick for hanging in there.You don't give up your the best How lucky we are to have you here. THANKS!

That good to hear you have it up and running again. This is not uncommon as most of the 2SC2166, 2SC1969 and 2SC2312 are fakes and made in China.