MK-328 TR/LCR/ESR Tester - UK Vintage Radio Repair and Restoration Discussion Forum

Sylvester · 1st Jun 2017, 9:35 am

This is my first post on your site. I recently purchased a MK-328 TR/LCR/ESR tester and unbeknown to me adjusted the screen contrast to such a level that I cannot read the display any more. Does anybody have any ideas as to how I can get the screen contrast back to a readable level? My thanks in advance for your assistance.

Freya · 1st Jun 2017, 11:14 am

Don't know your exact model but when the battery on mine gets low the contrast on the illuminated screen diminishes. Try a new battery maybe.
Failing that there will be a preset adjustment on the board, why it should change is a bit strange.

martiR2R · 1st Jun 2017, 2:02 pm

Press and hold the test button and a menu will appear.
Press and release repeatedly to scroll through the menu.
When you get to CONTRAST press and hold.
Press repeatedly to adjust contrast.
Press and hold to return to the menu.

Regards
Martin

Sylvester · 2nd Jun 2017, 1:13 am

Thank you for your comments. The problem I have is that I cannot see the characters on the display, hence cannot undertake your (Martin) suggested solution. It is through the adjustment of the contrast menu that got me into this mess. The contrast option only ramped down and wouldn't increment. I tried a number of actions with the single push button to try to get the unit to increment the contrast up rather than down but didn't succed. Hence I am in this mess. I was thinking of using the hardware reset but not sure how to do this and what would the consequences be? Help!

Thank you for your prompt response. I got into this mess because I used the contrast option, when I pressed it the contrast value started to decrement ( display loosing contrast), tried with the test button to reverse the contrast value but it kept on decrementing, now I cannot read the display. I thought of doing a hardware reset but am uncertain as to how to do this and what else this will affect. Help!

martiR2R · 2nd Jun 2017, 2:03 pm

" Contrast - This function is available for display controllers, which can adjust the contrast level withsoftware. The value can be decreased by a very short key press or left turn with the rotaryencoder. A longer key press (> 0.4s) or a right turn of the rotary encoder will increase thevalue. The function will be finished and the selected value will be saved nonvolatile in the
EEprom memory by a very long key press (> 1.3s)."

1. Make sure the battery is good.
2. Press and hold to access menu (1.5/2s NO MORE to long and it goes into normal test mode) which you can't see!
3. Then press 7 times (short), this SHOULD be CONTRAST (it's 7th on the menu list).
4. Then long press to enter contrast.
5. Now the tricky bit, a short press reduces contrast, a slight hold increases contrast, a longer hold saves the value. Each
press of around 0.5s should increase contrast by 1 notch.
6. Long press to save value and return to menu.

If this does'nt work go back to 2. and shorten press and hold.

Just played around with my tester and this procedure worked perfectly, however I CAN see the display!!

Good luck
Martin

martiR2R · 2nd Jun 2017, 7:49 pm

PS - I know you won't be able to see anything on screen, persevere. If at first........

Link below is to the designers'? notes (contains the contrast info I quoted in previous post).

www.g3src.org.uk/downloads/ttester_en.pdf

Sylvester · 3rd Jun 2017, 2:28 am

Martin, you are champion, when I am in England next time I will buy you a beer, Thank you very much for your help, your instruction worked perfectly. Further, thank you for the link to the designers documentation. Best Regards Sylvester

martiR2R · 3rd Jun 2017, 10:14 pm

Glad to have been able to help.

1st Jun 2017, 9:35 am	#1
Sylvester Retired Dormant Member Join Date: Jun 2017 Location: Whyalla, South Australia, Australia. Posts: 3	MK-328 TR/LCR/ESR Tester This is my first post on your site. I recently purchased a MK-328 TR/LCR/ESR tester and unbeknown to me adjusted the screen contrast to such a level that I cannot read the display any more. Does anybody have any ideas as to how I can get the screen contrast back to a readable level? My thanks in advance for your assistance.

1st Jun 2017, 11:14 am	#2
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,990	Re: MK-328 TR/LCR/ESR Tester Don't know your exact model but when the battery on mine gets low the contrast on the illuminated screen diminishes. Try a new battery maybe. Failing that there will be a preset adjustment on the board, why it should change is a bit strange. __________________ Stephen _________"It`s only an old telly" ___

1st Jun 2017, 2:02 pm	#3
martiR2R Hexode Join Date: Aug 2012 Location: Preston, Lancashire, UK. Posts: 344	Re: MK-328 TR/LCR/ESR Tester Press and hold the test button and a menu will appear. Press and release repeatedly to scroll through the menu. When you get to CONTRAST press and hold. Press repeatedly to adjust contrast. Press and hold to return to the menu. Regards Martin __________________ BVWS Member (lapsed!)

2nd Jun 2017, 2:03 pm	#5
martiR2R Hexode Join Date: Aug 2012 Location: Preston, Lancashire, UK. Posts: 344	Re: MK-328 TR/LCR/ESR Tester " Contrast - This function is available for display controllers, which can adjust the contrast level withsoftware. The value can be decreased by a very short key press or left turn with the rotaryencoder. A longer key press (> 0.4s) or a right turn of the rotary encoder will increase thevalue. The function will be finished and the selected value will be saved nonvolatile in the EEprom memory by a very long key press (> 1.3s)." 1. Make sure the battery is good. 2. Press and hold to access menu (1.5/2s NO MORE to long and it goes into normal test mode) which you can't see! 3. Then press 7 times (short), this SHOULD be CONTRAST (it's 7th on the menu list). 4. Then long press to enter contrast. 5. Now the tricky bit, a short press reduces contrast, a slight hold increases contrast, a longer hold saves the value. Each press of around 0.5s should increase contrast by 1 notch. 6. Long press to save value and return to menu. If this does'nt work go back to 2. and shorten press and hold. Just played around with my tester and this procedure worked perfectly, however I CAN see the display!! Good luck Martin __________________ BVWS Member (lapsed!) Last edited by martiR2R; 2nd Jun 2017 at 2:09 pm. Reason: Punctuation

2nd Jun 2017, 7:49 pm	#6
martiR2R Hexode Join Date: Aug 2012 Location: Preston, Lancashire, UK. Posts: 344	Re: MK-328 TR/LCR/ESR Tester PS - I know you won't be able to see anything on screen, persevere. If at first........ Link below is to the designers'? notes (contains the contrast info I quoted in previous post). www.g3src.org.uk/downloads/ttester_en.pdf __________________ BVWS Member (lapsed!)

2nd Jun 2017, 1:13 am	#4
Sylvester Retired Dormant Member Join Date: Jun 2017 Location: Whyalla, South Australia, Australia. Posts: 3	Thank you for your comments. The problem I have is that I cannot see the characters on the display, hence cannot undertake your (Martin) suggested solution. It is through the adjustment of the contrast menu that got me into this mess. The contrast option only ramped down and wouldn't increment. I tried a number of actions with the single push button to try to get the unit to increment the contrast up rather than down but didn't succed. Hence I am in this mess. I was thinking of using the hardware reset but not sure how to do this and what would the consequences be? Help! Thank you for your prompt response. I got into this mess because I used the contrast option, when I pressed it the contrast value started to decrement ( display loosing contrast), tried with the test button to reverse the contrast value but it kept on decrementing, now I cannot read the display. I thought of doing a hardware reset but am uncertain as to how to do this and what else this will affect. Help!

3rd Jun 2017, 2:28 am	#7
Sylvester Retired Dormant Member Join Date: Jun 2017 Location: Whyalla, South Australia, Australia. Posts: 3	Re: MK-328 TR/LCR/ESR Tester Martin, you are champion, when I am in England next time I will buy you a beer, Thank you very much for your help, your instruction worked perfectly. Further, thank you for the link to the designers documentation. Best Regards Sylvester

3rd Jun 2017, 10:14 pm	#8
martiR2R Hexode Join Date: Aug 2012 Location: Preston, Lancashire, UK. Posts: 344	Re: MK-328 TR/LCR/ESR Tester Glad to have been able to help. __________________ BVWS Member (lapsed!)