Hello,
I recently built the RLN4008B and have been having some problems getting it to work. I realized that the Op Amp I was using to substitute the CA3140E wasn't working correctly. I am using a LM741. I looked at the spec sheet for the LM741 and it seems to match up almost exactly to the CA3140E. I was wondering if anyone else has used the LM741 in place of the CA3140E? Does anyone have any suggestions as to why it might not be working?
Thanks,
Dave
RLN4008B - Using LM741 in place of CA3140E
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ricciticcitembo
- Posts: 730
- Joined: Tue Feb 26, 2002 4:00 pm
No. No. No. The circuit calls for a VOLTAGE COMPARATOR.
NOT AN OP-AMP! (like the 741). An LM311 is THE ONLY
acceptable substitute in the RIB for the CA3140E which is NLA.
Motorola uses this chip too. It is in RLN4008 rev D.
I have the schematic for the revision D, and low and behold it
looks just like the discription for substitute CA3140E/LM311
Found on Batlabs site. As you can READ, the two chips are wired
differently, and ARE NOT pin for pin compatible, so they cannot
be directly substituted. You need to follow the directions on Batlabs, Or get the print for a RLN4008D.
Like Monty already said. THERE IS NO DIRECT SUBSTITUTE FOR THE CA3140E.
And furthermore, that is why the majority of "Clone" ribs Don't
work on "programming sensitive" radios, like the X9000 for example.
Where you got the idea to use a 741, I'll never know.
NOT AN OP-AMP! (like the 741). An LM311 is THE ONLY
acceptable substitute in the RIB for the CA3140E which is NLA.
Motorola uses this chip too. It is in RLN4008 rev D.
I have the schematic for the revision D, and low and behold it
looks just like the discription for substitute CA3140E/LM311
Found on Batlabs site. As you can READ, the two chips are wired
differently, and ARE NOT pin for pin compatible, so they cannot
be directly substituted. You need to follow the directions on Batlabs, Or get the print for a RLN4008D.
Like Monty already said. THERE IS NO DIRECT SUBSTITUTE FOR THE CA3140E.
And furthermore, that is why the majority of "Clone" ribs Don't
work on "programming sensitive" radios, like the X9000 for example.
Where you got the idea to use a 741, I'll never know.
Just to share my experience, I am using the '741' since many years ago.
I faced problems ONLY with the GM900 (but it works without any problems
with MC/MCS/MT/MTS radios). Just for this radio, I got some CA3140 to
make sure if this is the problem. I replaced the chip but didn't test it yet.
Tomorow I'll test the RIB, so we'll know positively if this was the cause.
I faced problems ONLY with the GM900 (but it works without any problems
with MC/MCS/MT/MTS radios). Just for this radio, I got some CA3140 to
make sure if this is the problem. I replaced the chip but didn't test it yet.
Tomorow I'll test the RIB, so we'll know positively if this was the cause.
For what it's worth, this place is supposed to have about 2000 of the ca3140E's
http://www.factorydirect.co.uk/fdcompon ... 3140e.html
http://www.factorydirect.co.uk/fdcompon ... 3140e.html
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ricciticcitembo
- Posts: 730
- Joined: Tue Feb 26, 2002 4:00 pm
The only other thing that comes to mind, is to recheck all of the
transistors, making sure they are still "good", and that the PNP's
and NPN's are all in the proper locations. Also if using generic or
Radio Shack transistors, be sure to check the hfe (Beta) on ALL
of the transistors prior to using them. a value of between 100-200
should be OK. A beta of 5 on one transistor, and 370 on the other
in a complementary pair would be a bad thing. Also it is a common
thing for the Beta to vary as much as previously mentioned in a
surplus bag 'o transistors. It is normal.
Other than that, All I can tell you, is for sure the circuit on Batlabs
IS the real deal, and if you build it corectly, with NO part substutions, it will work. You can have faith in that. I built a couple
of them, even one with dual power supplies in an MX300 case. And
they all work flawlessly on EVERY radio that can be programmed by the rib.
Surpassing any "clone" rib. Especially for the older more difficult
radios. Thats what led me to build the rib in fact. The clone I had
bought worked on the vast majority of radio's, but not all.
transistors, making sure they are still "good", and that the PNP's
and NPN's are all in the proper locations. Also if using generic or
Radio Shack transistors, be sure to check the hfe (Beta) on ALL
of the transistors prior to using them. a value of between 100-200
should be OK. A beta of 5 on one transistor, and 370 on the other
in a complementary pair would be a bad thing. Also it is a common
thing for the Beta to vary as much as previously mentioned in a
surplus bag 'o transistors. It is normal.
Other than that, All I can tell you, is for sure the circuit on Batlabs
IS the real deal, and if you build it corectly, with NO part substutions, it will work. You can have faith in that. I built a couple
of them, even one with dual power supplies in an MX300 case. And
they all work flawlessly on EVERY radio that can be programmed by the rib.
Surpassing any "clone" rib. Especially for the older more difficult
radios. Thats what led me to build the rib in fact. The clone I had
bought worked on the vast majority of radio's, but not all.