President Ronald - Lo Bands Problem

A forum for the discussion of matters of a technical nature. All such activities are undertaken at the readers discretion and own risk. If you don't know what you are doing, don't blame us if it all goes wrong!
Post Reply
Phuture
Super Member
Super Member
Posts: 113
Joined: 04 Nov 2012, 14:01

President Ronald - Lo Bands Problem

Post by Phuture » 15 Oct 2018, 18:24

Hi,

I've got a President Ronald (EPT360011Z PCB) that under a certain condition fails to change frequency (stuck around 27.971 MHz) or transmit when switched to the "Lo" bands; however, on the "Hi" bands it appears to function normally. Based on a few T1 posts I found on here, I believe I have a President Ronald 1 as the PCB version is EPT360011Z and it's 6 band.
Superstar 3900 (High Band) 25615-28305 P1.jpg
I attempted carrying out a full alignment, as per the French version of the service manual and a little of the Secret CB Superstar 3900 (Hi Band) alignment procedure, to see if somehow the PLL was out of lock for the low bands but I initially hit a problem when trying to confirm AM, Band A, Channel 7 is 2.0V (TP2, R109). Secret CB advises the check is 2.2V on Channel 1, but this doesn't change the result. The voltage I get is over 8V on Bands A to C, on any channel even though I've successfully set the radio via L17 to 5.0V on Band F, channel 40, as per the service manual. As I say, the Hi bands, D to F, appear to be responding normally to band and channel changes, though I've not carried out a full channel-to-frequency check yet.

Anyway, I had the radio turned off overnight and returned to it to continue to troubleshoot. On turning on, the low band channels and complete function, including transmit, were working :!: So, I tried to continue with the alignment and found I was able to confirm 2.0V (TP2 R109) on AM, Band A, channel 7 and roughly 2.2V on channel 1 (Secret CB procedure). So far, so good. So then I go to the next step, which is to connect the FC to TP3 (R74); set AM Clarifier centred, Band C, Channel 19; and then adjust "A" to obtain 16.040 MHz 9 (according to Secret CB). This setting appears to be quite off and drifting rapidly between 16.04746 and 16.04755 MHz so I bring it back down to 16.040 MHz, but its still bouncing around this frequency. I then switch to USB for the next step and that's when the frequency counter jumps to 17.27995 MHz and stays thereabouts no matter where the mode switch is set. The radio's frequency counter is then back showing around 27.971 MHz and changes only the last digit, plus or minus a few kHz, up or down, but not stably or consistently. I then switch the radio off and on - no change - then off for an hour to let it cool down. Switching it back on restores a functioning low band setting again. Looking at the FC I can see that the 16.040 MHz I set earlier has jumped to over 16.042 MHz and rapidly drifting up to around roughly +/- 500 Hz. Leaving the radio to warm up, it drifts down to about 16.0385 MHz, so I bring it back up to 16.040 MHz, or thereabouts as it jumps and falls up to around +/- 300 Hz. Then, switching from AM to USB causes the problem all over again and the FC to show 17.27995 MHz (TP3, R74) and the on-board FC to show 27.971 MHz. By the way, the radio will receive on 27.971 MHz, just not change with the channel selector. It'll change a little, as I mentioned, but seemingly randomly by just a +/- 1kHz, so I can still here my mod tone for instance.

I'm guessing I may have a problem with the 14.010 MHz xtal but would appreciate some expert advice on this if possibe?

Cheers
You do not have the required permissions to view the files attached to this post.

User avatar
1968neil
Regular
Regular
Posts: 23
Joined: 17 Sep 2018, 21:30
Location: Buckinghamshire

Re: President Ronald - Lo Bands Problem

Post by 1968neil » 16 Oct 2018, 09:06

I would try changing C120 to 270pf and C75 to 56pf (use NP0 caps), then performing a re-alignment of the 14 MHz oscillator in accordance with the service manual.
Remove the KIA6410S (IC10) and replace it with a genuine Toshiba TA7310, this will improve stability no end.
For some reason the KIA6410S is not a very stable device maybe a cheaply produced component ?
The set up is critical, follow the manual to the letter and you should be good to go, if you haven't got proper test gear then i'd suggest having it set up professionally.
Good Luck :)

Regards
Neil

Phuture
Super Member
Super Member
Posts: 113
Joined: 04 Nov 2012, 14:01

Re: President Ronald - Lo Bands Problem

Post by Phuture » 16 Oct 2018, 09:50

Thanks for your reply, Neil

I've got proper test gear, so no issue there. Is IC10 inside the metal-canned sub-board module (sorry, I don't have the radio or schematics in front of me at present)? All the IC part number markings appear to have been removed with acid inside it.

I've just noticed that the white wire on the 3-wire (blue, red, white) link connector to the sub-board/module has detached from a solder tag, presumably from one of the rotary switches on the front panel. I'm not sure if this has just happened or has been detached for a while. It doesn't seem to have changed the current state of the radio, so perhaps it's been detached for a while. Would you or anyone know where I should solder this wire back to - most of the schematics I've found are a poor resolution, quality or don't show all the internal connections? Do you have a good copy yourself that you could share? A photo of the back panel wiring would be useful if anyone has one. :thumbup:

Thanks

User avatar
14CS06
Radio Addict
Radio Addict
Posts: 938
Joined: 04 Mar 2012, 09:15
Location: JN33LN - ALPES-MARITIMES-06 France

Re: President Ronald - Lo Bands Problem

Post by 14CS06 » 16 Oct 2018, 10:23

Hello

Please look at this post

viewtopic.php?f=26&t=53646

Image

Image

Image

Image

Image

Image

@+
Claude
Photo Collector CB RADIO

Phuture
Super Member
Super Member
Posts: 113
Joined: 04 Nov 2012, 14:01

Re: President Ronald - Lo Bands Problem

Post by Phuture » 16 Oct 2018, 16:14

Ah great, thanks Claude - all very useful. I've worked out the solder tag from one of your photos. Will solder it back on and feed back.

Phuture
Super Member
Super Member
Posts: 113
Joined: 04 Nov 2012, 14:01

Re: President Ronald - Lo Bands Problem

Post by Phuture » 16 Oct 2018, 20:42

Okay, so no change to the problem but at least the wire is soldered back on where it should be. I need to swap out the 7-segment LED channel display as I have an LED out on the second digit. The text printed on the side is "RI-DA45" but there's nothing on the underside. Would anyone know the direct replacement part code to replace dual digit 7-segment display (green) as I'm not finding anything under RI-DA45?

User avatar
14CS06
Radio Addict
Radio Addict
Posts: 938
Joined: 04 Mar 2012, 09:15
Location: JN33LN - ALPES-MARITIMES-06 France

Re: President Ronald - Lo Bands Problem

Post by 14CS06 » 17 Oct 2018, 07:53

Photo Collector CB RADIO

User avatar
cb4ever104
Veteran
Veteran
Posts: 4548
Joined: 28 Jul 2011, 21:26
Location: Alicante , España

Re: President Ronald - Lo Bands Problem

Post by cb4ever104 » 17 Oct 2018, 08:19

Phuture wrote:
16 Oct 2018, 20:42
Would anyone know the direct replacement part code to replace dual digit 7-segment display (green) as I'm not finding anything under RI-DA45?
I have green leds available here :

https://www.ebay.co.uk/itm/132822947351

If I were you the first thing I would do would be to recap the whole radio . I guarantee that that will solve some for those niggly issues around the VCO/local oscillator . After that it's a case of going through the manual , checking each mode and band as you go along. Those little fixed inductors on the AM/USB/LSB lines can give issues sometimes as well .

Cheers

Sammy
Last edited by cb4ever104 on 17 Oct 2018, 10:33, edited 1 time in total.
30TM060
Paul aka "Sammy". (108) PY60 Old Paisley DX Group (RIP Rab Markie)
Ex GM0 , now EA5 .
Handle "Fortune Hunter" back in "the day"
Radios ....? Anything that says "TAIWAN R.O.C" on the back.

User avatar
GusWroclaw
Regular
Regular
Posts: 21
Joined: 09 Oct 2018, 17:02
Call Sign: 161TM313
Location: Wroclaw, Poland

Re: President Ronald - Lo Bands Problem

Post by GusWroclaw » 17 Oct 2018, 09:33

Phuture are these voltages you mentioned the output of the phase detector? Or the input of the VFO? I'm asking out of curiosity.
161-TM-313 - Midland Alan 42

Phuture
Super Member
Super Member
Posts: 113
Joined: 04 Nov 2012, 14:01

Re: President Ronald - Lo Bands Problem

Post by Phuture » 17 Oct 2018, 18:50

Thanks all for your advice and suggestions. :thumbup: I managed to find a 7-segment green display replacement in a friend's scrap box , but thanks for the link cb4ever104 - I've saved it for future reference.

GusWroclaw, as per step 4 of the Secret CB alignment procedure attached (step 7 in French version), the voltage readings were taken at TP2, R109. R109 hangs directly off pin 7 of IC5 (MC145106P), the PLL frequency synthesiser, so the output of the phase detector.

User avatar
cb4ever104
Veteran
Veteran
Posts: 4548
Joined: 28 Jul 2011, 21:26
Location: Alicante , España

Re: President Ronald - Lo Bands Problem

Post by cb4ever104 » 18 Oct 2018, 07:38

1968neil wrote:
16 Oct 2018, 09:06
I would try changing C120 to 270pf and C75 to 56pf (use NP0 caps), then performing a re-alignment of the 14 MHz oscillator in accordance with the service manual.
Remove the KIA6410S (IC10) and replace it with a genuine Toshiba TA7310, this will improve stability no end.
For some reason the KIA6410S is not a very stable device maybe a cheaply produced component ?
The set up is critical, follow the manual to the letter and you should be good to go, if you haven't got proper test gear then i'd suggest having it set up professionally.
Good Luck :)

Regards
Neil
Just a couple of points . This radio doesn't use an IC packaged VCO . It uses a varicap .
Phuture wrote:
16 Oct 2018, 09:50
Is IC10 inside the metal-canned sub-board module (sorry, I don't have the radio or schematics in front of me at present)? All the IC part number markings appear to have been removed with acid inside it.
The metal canned sub board is the frequency counter board .

Cheers

Sammy
30TM060
Paul aka "Sammy". (108) PY60 Old Paisley DX Group (RIP Rab Markie)
Ex GM0 , now EA5 .
Handle "Fortune Hunter" back in "the day"
Radios ....? Anything that says "TAIWAN R.O.C" on the back.

Phuture
Super Member
Super Member
Posts: 113
Joined: 04 Nov 2012, 14:01

Re: President Ronald - Lo Bands Problem

Post by Phuture » 18 Oct 2018, 23:40

Very good point - thanks. Sammy. I guess the newer version of the schematic is what Neil was looking using for reference. Work on the radio is somewhat on hold until I install the channel display as I've remove the faulty one but not had a chance to install the replacement yet and the radio is currently on the bench in bits. Hopefully get to it this weekend to continue faultfinding the main issue. I'll check the caps around the xtals to see how they're holding up and decide then whether or not to they would seem to be root cause of the symptoms I've described.

Cheers very much

Tony

User avatar
cb4ever104
Veteran
Veteran
Posts: 4548
Joined: 28 Jul 2011, 21:26
Location: Alicante , España

Re: President Ronald - Lo Bands Problem

Post by cb4ever104 » 19 Oct 2018, 08:21

Hi Tony .

I had similar VCO problems with one of my old Taiwan Grants . I recapped it and it's like a new radio . I'm not saying that's your problem , but these early 11Z radios are getting on in age now , and for me new caps are a must .

Also . You'll be hard pushed to find a proper diagram for the 11Z . You can see that the one Clause posted isn't right as there's only one local oscillator in that one , and you have 2 . I posted some info here when I was working on my Franklin .

viewtopic.php?f=53&t=50627&hilit=EPT360011Z

To be honest most of the EPT3600 pcbs are pretty similar , but the LO/Hi band switching on the 11Z is a bit more complex .

Cheers

Sammy
30TM060
Paul aka "Sammy". (108) PY60 Old Paisley DX Group (RIP Rab Markie)
Ex GM0 , now EA5 .
Handle "Fortune Hunter" back in "the day"
Radios ....? Anything that says "TAIWAN R.O.C" on the back.

Post Reply

Who is online

Users browsing this forum: No registered users and 5 guests