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Digimax lite????

I was thinking of getting one for my TCR-458 wich is like new no mods.Do they give you instructions how to install in the 858 Board?
 
I put one in a TRC 458. The only problem was that the face plate sits so far from the chassis that the original knob won't fit back on as the new shaft is shorter than the original one. I couldn't find anyplace that sells a longer one of that exact type. I ended up taking a short piece of a Bic pen and heating it to make it fit tight over the new shaft to extend it. I also had to put a grommet in the face plate to remove any wobble. It works fine. The only complaint that I have is there is a buzzing after installing the DigiMaxLite. I contacted the company and was told be it was because of it being digital and suggested I buy a filter that they recommended for the incoming power to the DigiMax. I did that and it lessened it but it is still slightly noticeable. I later found the noise comes from the LED display as when I unplug the display from the main board it goes away completely.
 
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The filter shown would probably do the job.

Just make sure the display's circuit board is not grounded to the radio's metal chassis. The display must be mounted so that the board's ground foil is INSULATED from the radio's metal chassis.

We found that running the hot and ground wires all the way to the big filter cap near the rear of the circuit board shuts down most of the digit-scan noise. What you're hearing is the on/off switching current as the digits are scanned.

And if that big filter cap is approaching 30 or 40 years old, it could be time for a new one.

This has worked well for us.

73
 
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I never could get the squelch to work right on mine, this is what Mac sent me but there is no way this is the right squelch tap point...

Squelch tap is IC5 (MB3756) pin 5.
Use volt meter to work out if it's hi or lo and adjust R16 as per documentation.

Regards,
Mac

The squelch tap is tr15 on a cobra 140 gtl just like loose cannon told me... so I hooked it up to pin 5 of ic5 against my better judgement, then hooked it back to to tr15... I think I fried something hooking it pin 5 of ic5, because now when ever I turn the squelch all the way up the display goes blank. The voltage never changes on pin 5 of ic5 when you turn the squelch pot... if my memory serves me correctly it is about 12 volts or maybe it was 8 all the time
 
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The MB3756 contains three 8-Volt regulators and the transmit/receive switching.

Has nothing to do with squelch at all.

I would use the collector (center pin) of TR14.

You'll have to indicate the squelch polarity to the Digimax setup as high with squelch closed, low when squelch is open.

73
 
Do you think hooking up the squelch wire to 8 volts could hav fried something?. From what I remember it is squelch high... I haven’t messed with it for about two months now. I never could get r16 on the digimax board adjusted quit right . I would have to have the squelch pot turned almost all the way up to use the scan function.
 
The squelch circuit in this radio mainly uses a change in circuit current to open or close the squelch.

The actual up/down voltage change is not so large. Makes it harder for the scan function to tell the difference.

How important is the scan function for this radio?

73
 
The scan function is not that important to me personally... it just concerns that now after hooking it up to ic5, and then rehooking it to tr15. If I turn the squelch pot to far to the right the channel display completely blacks out... and I think the rx/tx light does as well, if I remember right. And it didn’t do that untill I tried connecting the squelch tap wire to pin 5 of ic5. Now if I leave the squelch pot turned all the way to the left the radio seems to work just fine.
 
Hi all,
Mac from Circuit Domain here, I have read previous posts and I feel I need to correct or reply to few before you guys over analyze things in the long run.
1. Yes, You can always reach me on Sales@CircuitDomain.com or just visit www.CircuitDoman.com site and shoot your questions to me via the website.
2. Yes, there is a humming noise on some (1%) of radios due to the fact that the radio was not designed to handle digital circuitry. Very few, but noticeably surfacing have an issue. The problem these radios have is not an RF issue, it is the power supply design issue. ie. driving multiple LED segments (depending on digits being displayed) causes the problem.
3. red97k1500 - Yes, I did send you the wrong information. MB3756 is where you pick up PTT not Squelch. I did spot this and sent you another email with correct information.
4. Shadetree Mechanic - Yes, prices are different in USD. I Don't have an "every hour" (not even every year) update on the current exchange rate set up for price comparison in my online shop. Thank you for pointing this out. I will fix it tomorrow, bit late here now.
However if you go through PayPal then you will always pay with current exchange rate even tho you used USD currency in my shop.
5. nomadradio - Thank you for pointing out that radio chassis is an independent floating GND. Well, RF GND, not common GND as "-"
And yes, your assumption in the way the squelch tap circuit is correct, In DigiMax Lite it is about Voltage difference (not current). The way this sensing wire is connected to the MCU via a voltage divider to arrive at no more than +5V DC. Never turn VR1 to it's extremes. Voltage at Pin1 of U1 must not exceed +5V
6. Allan, Thank you for your support. I have only just found this thread.
7. loosecannon - Encoders being used are exactly the same kind as any one else uses, I have had only one complaint that "it just fell apart when I touched it" over the last 10 years. go figure ;)
7. Any questions/problems etc. just email me Sales@CircuitDomain.com
P.S. OLED coming soon..
 
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