MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

Go to Thread: PreviousNext
Go to: Forum ListMessage ListNew TopicLog In


skootch13
aaron kuertz
cincinnati
(20 posts)

Registered:
06/30/2020 01:50PM

Main British Car:
1973 MGB Rover 4.6 (I'm told)

authors avatar
Calibrating 1973 MGB tachometer
Posted by: skootch13
Date: September 30, 2020 11:04AM

I have read the article on this site about soldering a potentiometer onto the chip inside the tach.

But the inside of my tach does not look like the one in the article.

i believe the article says to solder on posts 4 and 7 (going from memory.)

My question is, which of the posts on the chip are 4 and 7? How do you count them?
20200929_194609.jpg
20200929_194004.jpg
20200929_194247.jpg


skootch13
aaron kuertz
cincinnati
(20 posts)

Registered:
06/30/2020 01:50PM

Main British Car:
1973 MGB Rover 4.6 (I'm told)

authors avatar
Re: Calibrating 1973 MGB tachometer
Posted by: skootch13
Date: September 30, 2020 07:40PM

Leon reached out on mgexperience and told me that number one is next to the indentation on top of the chip.

Also, the correction on the pins in the article on this site is incorrect. It is pins 4 and 7 and not 3 and 8. Here is Leon's page [leonsmgb.com]

You can clearly see the indentation on the chip and also his leads on pins 4 and 7.


MGBV8
Carl Floyd
Kingsport, TN
(3980 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: Calibrating 1973 MGB tachometer
Posted by: MGBV8
Date: October 01, 2020 09:24AM

The confusion with the Figure 1 drawing stems from the capacitor being drawn in the wrong location (pins 3 & 5). The capacitor actually goes across pins 1 & 7.

[www.britishv8.org]


skootch13
aaron kuertz
cincinnati
(20 posts)

Registered:
06/30/2020 01:50PM

Main British Car:
1973 MGB Rover 4.6 (I'm told)

authors avatar
Re: Calibrating 1973 MGB tachometer
Posted by: skootch13
Date: October 01, 2020 01:19PM



MGBV8
Carl Floyd
Kingsport, TN
(3980 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: Calibrating 1973 MGB tachometer
Posted by: MGBV8
Date: October 05, 2020 09:02AM

This is the corrected version.
Zak's Tach Schematic Revised 2020.jpg


Sorry, only registered users may post in this forum.