CRT SS 7900 Service Mode

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gpo999
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CRT SS 7900 Service Mode

Post by gpo999 » 08 Apr 2016, 01:56

Power on pressing Menu and Mode buttons .

Through the channels except 1 to 3 and only 15 available (no values/error 1 to 3) then channels 4 to 15 if one sits on the channel and a quick single press of the channel selector brings up a value , press mode to go back previous view .

4 FRQ 0501
5 FRQ0F "blank"
6 BFO 0508
7 AFR 0519
8 CTSS 0038
9 DCS 0028
10 SUL36 0754
11 SUL01 0018
12 SFA36 0859
13 SFR01 0017
14 ASQ 0038
15 RsiTx 0047

What they do and apart from a "obvious" answer like , sets the BFO from the Peanut gallery , whats the go ?

I have seen mention like use a frequency counter on test point "whatever" and adjust the value for a "whatever" .

So anyone donate their knowledge in the finer details of the above ? , ctss/dcs/asq would not be a concern i think for my purposes but the others would be interesting to know about .
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Re: CRT SS 7900 Service Mode

Post by gpo999 » 08 Apr 2016, 04:11

Hi Cut not enough on this Radio?

Compared to the 8800 it's still a bit noisy , they use the same circuit but those smd capacitors are not marked on what they are .

In nearly all the older radios br9000/m8800/8900 and others on the schematics they use a 223 for high cut switched in by a transistor , i just finished testing and if i parallel another 223 with the one already there its nearly the same hi-cut as the m8800 , so i'm going to order some same size smd caps (really tiny) and do a proper job this time , the poor old maxlog mods has 603 style in where they should be the next size down .

edited>ps> there are red circles on those pictures center/right they do not show up as posted , one would have to zoom in?
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Re: CRT SS 7900 Service Mode

Post by gpo999 » 09 Apr 2016, 02:39

4 FRQ 0501

A quick check and Seems to be the one so far that'll put a 100hz low SSB tx with the clarifyer set on "R" back on frequency , set it to 0510 and it has not changed the "T" or "RT" clarifyer which was spot on .

It might be that every "10" might be 100hz and going up in numbers actually goes down in frequency ??

How do i check? , plugged in a pair of earphones , a mono to stereo 3.5mm adapter and use a known good receiver with either a dummy load or no antenna and back off the Rf gain , works every time .

Later on i'll be looking at all those numbered test points on the Pcb on the underside to see whats relevant with the highly accurate frequency counter and other stuff i have here .
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Last edited by gpo999 on 09 Apr 2016, 04:07, edited 2 times in total.
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Re: CRT SS 7900 Service Mode

Post by gpo999 » 09 Apr 2016, 03:59

Balanced Mixer/Modulator , yet to check it out as it'll be "Bench Day" in a week or so , same IC as used in the older radios m8800/br9000 excetera .
http://www.njr.com/semicon/PDF/NJM2594_E.pdf look at page 6 .

The VR W10 in the tin can should be the Carrier Balance ? but yet to find out .

I took a heap of pictures of the CRT 7900 when i had the covers off , now i'm going through them all on the computer and comparing the Maxlog and others to the schematics that i have accumulated over the years , it fun !
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Re: CRT SS 7900 Service Mode

Post by gpo999 » 09 Apr 2016, 09:42

BTW , RX current (Receiving LSB un-squelched) is 270 ma , the Maxlog M8800 for memory was 350 to 400 ma or a tad more .
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Re: CRT SS 7900 Service Mode

Post by gpo999 » 09 Apr 2016, 11:02

Been bashing the keyboard found these

AT6666
CH 04 FRQ 0485
CH 05 FRQOFF
CH 06 BFO 0506
CH 07 AFR 0451
CH 08 CTCSS 0041
CH 09 DCS 0027
CH 10 SQUL36 0005
CH 11 SQUL01 0008
CH 12 SQFA36 0005
CH 13 SQFA01 0008
CH 14 ASQ 0962
CH 15 RSSITX 0667

The last one 15 looks like TX meter power out , 05 looks like the display? or clarifiyer off? BFO is still bfo

The wording makes a big difference like below .

SS 7900
4 FRQ 0501 (mine now 0510)
5 FRQ0F "blank"
6 BFO 0508
7 AFR 0519
8 CTSS 0038
9 DCS 0028
10 SUL36 0754
11 SUL01 0018
12 SFA36 0859
13 SFR01 0017
14 ASQ 0038
15 RsiTx 0047

any more ideas? take a guess .
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Re: CRT SS 7900 Service Mode

Post by delboyonline » 09 Apr 2016, 18:19

SUL = Squelch settings for upper/lower sideband?
SFA = Squelch settings for AM/FM?
ASQ = Auto Squelch level?

On the Lincoln 2 BFO adjusts the frequency of individual modes, pressing the MODE button selects which mode is adjusted. This may be the same on this radio?

And again on the Lincoln 2 a lot of these settings can only be adjusted using a signal generator. The level of the input signal is used to set the value.

One last thing, PLEASE BE CAREFUL AS THESE SETTINGS CAN SERIOUSLY F##K UP YOUR RADIO!

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Re: CRT SS 7900 Service Mode

Post by gpo999 » 10 Apr 2016, 03:30

Ok thanks DELBOY (that was a good show out here) .

I see what you have typed , those squelch setting are not in the PC software or on board only ASQ via the normal menu so they make sense , not that i have to or need to fiddle with those anyway but its good the know just what they are anyway imo .

Ok on the BFO one , when the radio is on the bench sometime in the future and i'm looking at/for the test point numbers and what they represent what i'll check out that BFO one .

Ok too on the sig gen that'll be for the squelch settings , a frequency counter is used for the BFO for example and FRQ , on this radio if one is in the Service Menu the radio can still TX so one could use a receiver instead of a Freq counter in real time ie> no guessing what number (example- 0501 does).

One last thing is quite valid , one should write everything down first on several bits of paper and fiddle minimally .

Turning out to be a long post and a coincidence as i came across this 10 hours ago or more , here https://simonthewizard.com/2014/08/26/p ... chematics/ and studied the **** out of it .
Is not the exact schematic for the SS7900 but its so close to it and the best so far it should do for looking about if one likes that sort of thing (i do) , apart from a few differences its good enough for the M8800/Br9000/all the 5000's and others 6666 , its like back in the old days with the 02A Cybernet chassis's , all different radios on the outside were made and many of them all using the Cybernet board most with slight or sometimes very big differences .
cheers .....
Last edited by gpo999 on 10 Apr 2016, 07:56, edited 1 time in total.
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Re: CRT SS 7900 Service Mode

Post by Admiral » 10 Apr 2016, 06:49

delboyonline wrote: One last thing, PLEASE BE CAREFUL AS THESE SETTINGS CAN SERIOUSLY F##K UP YOUR RADIO!
I may be wrong (no change there then?) but I believe that if you shag up these 'secret' settings then a factory reset won't help you as they get stored in flash somewhere and the reset doesn't alter them. So yes, before twiddling write down all the values legibly, better still take photos, and only twiddle if you need to.

This is not a reference to you gpo999 because you appear to know what you're talking about, just a friendly warning to the many guests that view our forum.
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gpo999
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Re: CRT SS 7900 Service Mode

Post by gpo999 » 10 Apr 2016, 07:57

I think your spot on Admiral .
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Re: CRT SS 7900 Service Mode

Post by delboyonline » 10 Apr 2016, 20:16

Admiral wrote:
delboyonline wrote: One last thing, PLEASE BE CAREFUL AS THESE SETTINGS CAN SERIOUSLY F##K UP YOUR RADIO!
I may be wrong (no change there then?) but I believe that if you shag up these 'secret' settings then a factory reset won't help you as they get stored in flash somewhere and the reset doesn't alter them. So yes, before twiddling write down all the values legibly, better still take photos, and only twiddle if you need to.

This is not a reference to you gpo999 because you appear to know what you're talking about, just a friendly warning to the many guests that view our forum.
Yes mucking about with these settings can cause serious problems with the operation of the radio.

It was said by others that many people wrecked their Lincoln 2's after I posted the very first video about the hidden menu although NOT A SINGLE PERSON CONTACTED ME about doing so!!!! Not surprising as I didn't actually show how to access the menu at that time.


Anyway it's best to leave well alone unless you have the proper gear to put it right if you mess it up!!!!!

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Re: CRT SS 7900 Service Mode

Post by gpo999 » 11 Apr 2016, 01:46

Or another way of putting it is

Why be a Plonka and fiddle with stuff ya ain't got a clue about

or something to that effect .
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Re: CRT SS 7900 Service Mode

Post by gpo999 » 11 Apr 2016, 01:48

05 AFR , Maybe Audio Frequency Receive gain? (setting the front volume control min/max)

The wording on this stuff puts one out , The AM ANL vr on the board suggests automatic noise limiter for receive , but its way up there close to the power settings .

So a tweak with it found out its AM modulation audio TX and easily overdrives even though there is a AM MOD one down at the bottom right of the pcb which also works but very minimally , the main one is AM ANL .
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Re: CRT SS 7900 Service Mode

Post by gpo999 » 11 Apr 2016, 06:57

Like this for instance .
W8 AMANL is not on the Lincoln schematic when i took a quick look , the BR9000 schematic shows W10 AM AMC in a different area , its not the exact circuit as things have changed over the years but it's still close to the W8 AMANL which "is" the AMC i gather ..
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Re: CRT SS 7900 Service Mode

Post by TeamFabulous » 16 Nov 2016, 19:49

Does anyone know how to turn the RF meter up as mine reads very low even on full power!

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