Links correct now. So, you can see from the mic socket pic, that if you unplug the mic and short pins 5 & 3 (or 5 & 4) this will set the rix into RX mode which basically switches on the speaker.

The audio amplifier IC for this rig is - KIA 7217 - according to the Knightcb website they cost about £3.45
 
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Clanforbes said:
Links correct now. So, you can see from the mic socket pic, that if you unplug the mic and short pins 5 & 3 (or 5 & 4) this will set the rix into RX mode which basically switches on the speaker.

The audio amplifier IC for this rig is - KIA 7217 - according to the Knightcb website they cost about £3.45
Click to expand...


Thanks Matey

I have pulled it out of the landy tonight and i am planning to look at it at work tomorrow as i had another boring day planned
 
Ok so an update, i have just checked the mic and found that the earth had come off so now i have sound when the unit is on, i get white noise when the squelch is around min and then nothing when moved to max is that correct?
 
yep, the white noise should cut off at around 1/3 to 2/3 turn of the knob. Excellent, this means your audio amp is ok, chances are the rest of the innards will be too. Audio amp and reverse polarity diodes are the most common faults on these wee rigs because some muppet wired it wrong way round, apart from that you get some which suffer from dry joints. For my own rigs, I like to solder in a bridge rectifier to eliminate any chance of accidental wrong polarity if loaning them out.

Now all you need to do is sort out the antenna.
 
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Ere Clan - do you repair rigs then - coz i gorra dodgy one - seems to fail transmit after a variable time.... Q is - is it worth repairing?
 
Hi MHM.

I used to do a lot of rig repairs but gave it all up a good few years ago, though I do still have all my old test gear and diagrams.

Please don't say it's a Maycom EM-27 with an orange display (or was it the green display that was a bucket of ****e?) Personally, I'd recommend Knightscb for any repairs as long as it's a standard rig which hasn't been doctored to add more channels. If it's been doctored, they will NOT touch it under any circumstances.

As for whether it's worth repairing or not, if it's an Amstrad 901 or a Rotel (or any other Cybernet based rig) then most definitely get it repaired. Many people also love some of the older Audioline rigs which are built around the Uniden board, so this would also be a definite yes (I was never very fond of them as the audio is a bit too bassy for my taste, but excellent for the higher pitched female voice.) If it's one of the crappy little rigs then it would depend on what the problem was (could be a 50p repair job for an output transistor,) even the old DNT's, which were hated by most but could be doctored to do an awful lot of things, might be well saught after by those in the know.
 
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**** me, Mr Forbes - r u the bastid that sold it to me ;). how did you know - i just checked - yup its an EM-27 with orange display :mad:

i take it its crap then - fit for bin?
 
I also have a hardly used Maycom EM-27. Fantastic little rigs, very pretty and work well - until they develope the failure to TX syndrome. I sent mine to Knights for repair and it came back working, but only lasted a few months.

The man who finally finds the permanent solution to this problem with them will have a golden statue erected in his honour. I'd love to bin mine, but just cannot bring myself to do it, one day, maybe, someone will solve the problem. Last time I checked a few months ago, it was still a mystery.

Oh, and the green display ones are the updated version, which as far as I know do NOT suffer from the same problems.
 
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as yu say - brill rig - i have replaced it with a green screen version - praying its better :eek:.

I take it Maycom aint interested?
 
I don't know if anyone has tried Maycom, I've never heard of anyone that has. My EM-27 worked for years on a daily basis. The original ones have a small battery on board which retains the setting in the memory when not in use. When I laid mine up for a while, the TX problem appeared shortly after starting to use it again. When knights repaired it for me, one of the upgrades that is advised is to replace the battery with a large capacitor which will keep the memory alive for a reasonable time. Again, the rig worked well for me for a good few months, but I laid it aside again and then the same problem appeared. Theoretically then, it must have something to do with the volatile memory on board losing power then things go wonky. Personally, if I was gonna be using mine again on a regular basis, I'd send it off to Knights for repair again (I do not know what they do to get it going again) and make a point of keeping it alive by regular use. This is only my theory, if it was that simple I'm sure someone more knowledgable than me would have found the cure by now, but personally, I'd be prepared to risk the cost of a repair (I think it was about £20 to £30 last time, but am not sure) as it is a superb little unit, as long as it kept going, but THAT is the big question, would it keep going troublefree?

Good luck whichever you decide.
 
The Mad Hat Man said:
**** me, Mr Forbes - r u the bastid that sold it to me ;). how did you know - i just checked - yup its an EM-27 with orange display :mad:

i take it its crap then - fit for bin?
Click to expand...

How did I know?

Easy, there are a **** of a lot of them out there waiting for someone to find the permanent cure and it's the only rig I've heard of that does this on a regular basis, some minor mis-alignment of the VCO settings can cause almost any rig to show these symtoms, but is easily rectified by proper adjustment of the VCO (voltage controlled Osccilator.):D:D:D:D
 
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Just had a quick nosey on Ebay, there are two Amstrad 901's on sale just now - the first has only 42 mins to go when I looked.

Nope, neither are me selling them.

Amstrad rigs are superbly reliable, easily repaired (I repaired one which had a 2" inch hole burnt into and through the printed circuit board,) and can be tweaked quite a bit - not that I condone this kind of thing. Getting some of the parts might not be quite so easy now though, the audio amplifier is the LA4422, I think they are getting rare, though Knights still have them at £2.95 so can't be too bad yet.
 
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Just got a new rig so should do for play days. an old midland rig with a 1.3m centre load and on a clamp but sod the swr meaiter when t have a TUAM siting wonder if it will work?
 
Help

Right I have a new mic and all is working well with the unit until I try to swr it. I have earthed my antenar to the battery terminal to se if it makes a difference and it dosnt here is the problem.

Connected swr as per instructions

Pressed resever and adjusted the swr meter to the set point on channel 40 using the cal knob

Switched it over on the swr meter to take reading and it is slightly lower than the set on channel 40 and then still half way in the red on channel 1

What do I do now?
 
First of all, use the SWR meter correctly.
Switch it to *FWD* press the mic and adjust the needle to align over SET on the scale, now release the mic, switch to *REF* then press the mic again for the reading. complete this on both channel 1 and channel 40 to find out which is the worst.

Once you get the readings near to mid range, the rule of thumb is; which ever reading is the worst, then adjust from that. ie; if channel 1 is the worst, you need to lengthen the aeriel slightly (bit at a time) if channel 40 is the worst, you need to shorten the aeriel, do this until both reading are the same.

There are certain scenarios were you will not get a good SWR reading depending on location of the aeriel mounting, or type of aeriel used.
 
Hi again Bob,

First, as Gaffer suggested, check you are using the SWR meter correctly, though I'm pretty sure you probably are.

Next, What antenna are you using?

Have you checked it as I suggested above with your multi-meter for either short circuits and/or open circuits?
If nothing obvious or ominous shows up, I would start by stripping the entire antenna and it's mounting down and cleaning everything, most common problem is rusty earth connection where the braid is screwed to the base on a mag mount (I know your's isn't a mag mount) corrosion within the base of the antenna where the whip goes into the base, which can cause a high impedence and destroy the signal.
Next most common cause of failure is a single strand of either the braid or the inner core (if multi-stand) causing a short (this would show up with multi-meter checks and coul;d be at the PL plug or antenna base.)
Third common cause is dirt/mild corrosion on the end of the whip, take the whip out, clean the end of the whip with wire wool and try to scrape the inside of the hole it goes inmto with a suitable sized drill bit.
Finally, I have come across a few antennae which have had a bit missing off the end of the whip (tree/bridge strike.) Carefully examine both ends of the whip to see if it looks like a bit has broken off (usually a sharp or rough end.)

Have fun.
 
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