Unless it has a switchmode power supply, very unlikely, why are you replacing all the caps ?
Have you actually checked the DC Supply Voltages ?
When ya dig out a 70cm radio you had from the late eighties and it dont go .
No use since life led to music and drumming and...
Ordered every cap from wes and none will fit .The electros now are skinnier and taller.
Wont give up and I dont like tantalums as ive seen so many stuffed.
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Unless it has a switchmode power supply, very unlikely, why are you replacing all the caps ?
Have you actually checked the DC Supply Voltages ?
tristen (17-08-18)
Decided to do it due to the age factor before faultfinding the no transmit issue.
Its a Kenwood TM401 and have a manual with block diagram and schematics.
Will prolly start fault finding now instead of changing all the electros first
One of the problems created by 'replacing all the caps first' is that you have introduced a new set of conditions without finding the actual fault.
Whilst age does cause some caps to change in value and/or have elevated ESR readings, this is not a hard and fast rule and in much of the vintage equipment that I service
the original caps are still performing perfectly after 30+ years.
i never start to fault find on these without leaving them on for a couple of days makes life much easier
tristen (21-08-18)
Agreed.
Replacing components without first having established the actual culprit can fool you into thinking that you have located and fixed the problem when you haven't and in general, is not good fault-finding technique.
(Having said that, I well remember the days when it was standard practice to replace all coupling and decoupling capacitors - but with good reason).
Yes, and soak testing also has its place.
First of all it never makes me angry if I need to fix something, especially an almost vintage device. I enjoy the challenge.
Second there is no need to soak anything if the there is no TX. RX is a different story.
Just get straight onto the job. TX is very straight foward. Track the supply, solder joints and copper around the larger parts, anything that is socketed and the caps with an ESR meter. If the service manual shows the voltages in TX state then you should be able to nail it down pretty quick.
And don't forget a dummy load.
Last edited by Uncle Fester; 22-08-18 at 11:00 AM.
Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...
Stopped ordering capacitors from WES some time ago. Catalogue presents one physical dimension, yet the part is substituted with another.
Also found the repairs would bounce not long after.
Perhaps their quest to compete with other suppliers has resulted in sourcing parts from less than reputable vendors?
Agree with the dislike of tantalums; they are a curse.
"The saddest aspect of life right now is that science gathers knowledge faster than society gathers wisdom." - Issac Asimov
Thanks guys its fixed Now to get my callsign back and renew license.
Cheers all !!
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