Ranger 2950dx cpu board options

[Edd200sx]

So I had a blown cpu ept695042z

I fitted a dpt295042z

everything works except there is no speaker sound
Or receive

all the connections are numbered the same but the new board doesn’t have echip only jumper to wideband it which is working.

the radio died from a short circuit in the beginning

I’ve noticed there’s no voltage on middle pin of rx transistor but tx side works fine.

Could it need modifications to work with this cpu?

 

[Edd200sx]

Edit. I have no 8v rx line…

 

[nomadradio]

I have no 8v rx line…

The receive transistor Q47 is a PNP with the emitter connected to 8 Volts. The collector (center pin) is the receive-mode output. The voltage on the base leg is the key here. If it's more than 6/10 of a Volt below the emitter voltage, Q47 is probably bad. Typical reading for a bad Q47 is zero Volts on the base terminal while receiving.

If you want to check the receiver alone, you can bridge across from the emitter of Q47 to the collector, like with a pair of thin hemostats. You don't want to key the mike while doing this, but it would let you see if the receiver actually works with the correct receive-mode voltage feeding into it.

73

 

[Edd200sx]

Thanks buddy

I’ve changed q47 for another second hand one

although if I bridge it I do get rx back

guess it’s another duff one

The receive transistor Q47 is a PNP with the emitter connected to 8 Volts. The collector (center pin) is the receive-mode output. The voltage on the base leg is the key here. If it's more than 6/10 of a Volt below the emitter voltage, Q47 is probably bad. Typical reading for a bad Q47 is zero Volts on the base terminal while receiving.

If you want to check the receiver alone, you can bridge across from the emitter of Q47 to the collector, like with a pair of thin hemostats. You don't want to key the mike while doing this, but it would let you see if the receiver actually works with the correct receive-mode voltage feeding into it.

73

 

[Edd200sx]

Swapped for another good q47 still no rx

it must be a wiring difference between the CPU’s

 

[nomadradio]

No, it's not a wiring difference. You have a zener diode and another transistor that drive the base of Q47.

Having a way to test parts does reduce confusion.

Pin 7 of IC6 should be at least 6 Volts in receive mode, usually a Volt or so higher than that.

This drives into R222 and D64. They feed current into the base of Q48.

If you have around 2/3 of a Volt on the base lead of Q48, next place to check is the collector of Q48. Should be less than one Volt.

And if you don't have any voltage on the base of Q48, the problem is upstream from there, R222 and/or D64.

When Q47 failed, it could have shorted internally and fed surge current into the collector of Q48 and blew it out.

Maybe.

73,
Chris

 

[Edd200sx]

Many Thanks Chris I will go through the suggestions

rgs

 

[Edd200sx]

I’ve got it working Chris was a bunch of dry joints.

only fault I have now is ssb rx is quite low

I’m guessing check q23/25?

Maybe the diode next to L12

rgs

No, it's not a wiring difference. You have a zener diode and another transistor that drive the base of Q47.

Having a way to test parts does reduce confusion.

Pin 7 of IC6 should be at least 6 Volts in receive mode, usually a Volt or so higher than that.

This drives into R222 and D64. They feed current into the base of Q48.

If you have around 2/3 of a Volt on the base lead of Q48, next place to check is the collector of Q48. Should be less than one Volt.

And if you don't have any voltage on the base of Q48, the problem is upstream from there, R222 and/or D64.

When Q47 failed, it could have shorted internally and fed surge current into the collector of Q48 and blew it out.

Maybe.

73,
Chris

 

[nomadradio]

I would first make sure that L10, L11 and L12 all show a proper peak.

That's not a common symptom on that circuit board, so that's where I would look first.

73

 

[Edd200sx]

I would first make sure that L10, L11 and L12 all show a proper peak.

That's not a common symptom on that circuit board, so that's where I would look first.

73

thanks Chris

they seem ok. If I touch the q23 area the rx goes up but not to full sensitivity then if I reduce the generator then increase it doesn’t recover the signal again.

changed q23/25 and the diode i mentioned before.

am fm is spot on very sensitive


Rgs

 

[Edd200sx]

It has the L10-11-12 cans from a known working radio in it and still deaf on ssb.

Q23 is the problem I’m sure

if I touch this leg with anything conductive the rx
Comes up quite a bit. But again this is a known working part so I guess the voltage is dragged out somewhere along the line

 

[Edd200sx]

Off to the spares bin.

at least I can use the cpu in something else.