Tr4aJim Posted February 15, 2022 Report Share Posted February 15, 2022 Folks, I want to replace the VS on my TR4A (negative ground). My initial plan was to get one of the new solid state units from either The Roadster Factory, or Moss (US). However several folks on the Triumph Experience forum have said the VS units being offered by the US vendors are very trouble prone (one gentleman had 4 bad units in a row from Moss). Have you gents had better luck with any of the VS units offered by your suppliers? thanks Jim Quote Link to post Share on other sites
RogerH Posted February 15, 2022 Report Share Posted February 15, 2022 Hi Jim, I fitted a Moss VS about 10 years ago and all is well. However that does not mean that current ones are as good. They are such simple items and should be internally protected. As they are quite cheap why not give it a go. Roger Quote Link to post Share on other sites
keith1948 Posted February 15, 2022 Report Share Posted February 15, 2022 (edited) Hello Jim Make sure that the electronic solid state version you get is marked -GND on the back for negative earth cars. A while ago over here in UK, Moss were selling +GND units but using the wrong part number for the negative ground units. From their data sheet I got it states 131-555 negative ground 131-556 positive ground The older original non solid state units work regardless of polarity. I have one of those. Here is a link to a thread I started 3 years ago on this topic https://www.tr-register.co.uk/forums/index.php?/topic/66848-voltage-stabilisers-for-tr4-and-4a-are-different/ Keith Edited February 15, 2022 by keith1948 link to earlier thread Quote Link to post Share on other sites
Tr4aJim Posted February 15, 2022 Author Report Share Posted February 15, 2022 Keith, thanks for that tip. As Roger says, they’re not expensive so I’ll try one and verify it’s marked for negative ground. Jim Quote Link to post Share on other sites
lynchpin Posted February 15, 2022 Report Share Posted February 15, 2022 (edited) Hi Bought a positive earth solid state one from an advert on e bay about 14yrs ago from a bloke who made them himself, its been fine all this time, that's jinxed that now I expect.. Phil... Edited February 15, 2022 by lynchpin Quote Link to post Share on other sites
rogerguzzi Posted February 15, 2022 Report Share Posted February 15, 2022 Hello All I just bought a few of these and fitted them inside the original can (Negative for Spitty) been working for 10+ years LM7810ACT Onsemi, Linear Voltage Regulator, 7810, Fixed | Farnell Roger Quote Link to post Share on other sites
Tr4aJim Posted February 15, 2022 Author Report Share Posted February 15, 2022 I just found this on eBay. If it’s NOSit might be worth the price. https://www.ebay.com/itm/175116901848?hash=item28c5c7ddd8:g:s-EAAOSwSQ9h5ySQ Jim Quote Link to post Share on other sites
RogerH Posted February 15, 2022 Report Share Posted February 15, 2022 Hi Jim, in theory the solid state VS is bomb proof. It could be improved but at a cost. The original Lucas thermal VS is nearly bomb proof but the contacts will wear out one day. Stick with the Solid state VS. Roger Quote Link to post Share on other sites
Tr4aJim Posted February 15, 2022 Author Report Share Posted February 15, 2022 Hmmm, good idea, thanks Roger. Jim Quote Link to post Share on other sites
rogerguzzi Posted February 15, 2022 Report Share Posted February 15, 2022 Hello All This what I fitted in Spitty ,Vitesse and TR6 some negative and some positive. They are a cheap as chips and easy to fit! 6 X Regulator Voltage L7810CV LM7810 7810 10V 1,5A - Voltage Regulator TO-220 692685035738 | eBay Roger Quote Link to post Share on other sites
RogerH Posted February 15, 2022 Report Share Posted February 15, 2022 If you have a POSITIVE earth then you need the LM 7910 Roger Quote Link to post Share on other sites
RobH Posted February 15, 2022 Report Share Posted February 15, 2022 (edited) As the two Rogers say, it is easy to build one into an old casing: The LM 7810 works for negative earth cars, the LM 7910 is for positive earth. The connections are very simple and it only requires a couple of other components. These are 0.22uf ( 220nf ) capacitors from the input terminal to earth and from the output terminal to earth to help with noise isolation. The voltage rating of these is not important as long as it is higher than 50 volts, most such capacitors are higher. These ones are fine: https://www.ebay.co.uk/itm/263756115737?hash=item3d6916ef19:g:CG8AAOSw1u5bIYJz&var=562973822517 Some makers may fully encapsulate the chip including the mounting tag. In that case a wired earth connection is required to the centre pin. Edited February 16, 2022 by RobH added comment Quote Link to post Share on other sites
stillp Posted February 15, 2022 Report Share Posted February 15, 2022 The 78 and 79 series regulator ICs do get hot, so they need to be firmly clamped to the metal case with a smear of heat sink compound. In the late 70s I was involved with developing solid state voltage stabilisers for the company I worked for, who were trying to get into automotive electronics, and we found there was a lot of difference between different manufacturers in terms of reliability and ability to handle high temperatures and voltage transients. Sadly I can't remember which ones were good, but it's probably all changed now anyway. I think I was named on the patent application, but I never did receive any royalties! Pete Quote Link to post Share on other sites
RobH Posted February 15, 2022 Report Share Posted February 15, 2022 You are right they need clamping to metal but they shouldn't get terribly hot in this application Pete - the gauges don't draw much current - around 200mA total - and the regulator is dropping less than five volts max, so the dissipation is only about 1 watt. Quote Link to post Share on other sites
stillp Posted February 16, 2022 Report Share Posted February 16, 2022 10 hours ago, RobH said: You are right they need clamping to metal but they shouldn't get terribly hot in this application Pete - the gauges don't draw much current - around 200mA total - and the regulator is dropping less than five volts max, so the dissipation is only about 1 watt. Agreed Rob, but 1W is rather a lot for an enclosed TO220 package. Pete Quote Link to post Share on other sites
rogerguzzi Posted February 16, 2022 Report Share Posted February 16, 2022 15 hours ago, stillp said: found there was a lot of difference between different manufacturers in terms of reliability and ability to handle high temperatures and voltage transients. Hello Pete I must have bought the good ones as still ok after 10years! I did clamp it to the aluminium case probably with a smear of heat paste? Roger Quote Link to post Share on other sites
c.hydes Posted February 18, 2022 Report Share Posted February 18, 2022 My TR6 fuel and temperature gauge have always seemed to read low. Measured my TR6 V.S. yesterday, using an AVO model 8 analogue meter. Oscillates about every second between 7 to 9V dc at 12.5V input . I believe I read somewhere that it can be adjusted with a screw that increases or decreases the gap to the thermal bi-metallic strip. Is this true, as could be reason gauges read low? Colin. Quote Link to post Share on other sites
RobH Posted February 18, 2022 Report Share Posted February 18, 2022 (edited) See this. Most don't have the adjustment screw available: http://www.mgb-stuff.org.uk/ivs.htm Your AVO reading is only approximate and depends on the inertia of the needle as it wobbles between zero and 12v. To get a proper reading you need to smooth the voltage using an RC network as shown at the end of that link. The output from the bi-metallic stabiliser is a square wave switching between 0v and supply voltage with variable mark-space ratio depending on the value of the supply. The car meters average that output thermally and you either need a true-rms reading meter or a smoothing network to read the right value. An AVO only reads true rms on the ac volts range for a sinewave input. Edited February 18, 2022 by RobH Quote Link to post Share on other sites
c.hydes Posted February 18, 2022 Report Share Posted February 18, 2022 Thanks Rob, I will remeasure with the RC network firstly and if necessary see if it has the adjustment screw fitted. Colin. Quote Link to post Share on other sites
RobH Posted February 18, 2022 Report Share Posted February 18, 2022 I should also have said that with the smoothing network, you use the AVO on the dc voltage range of course. Quote Link to post Share on other sites
c.hydes Posted February 18, 2022 Report Share Posted February 18, 2022 42 minutes ago, RobH said: I should also have said that with the smoothing network, you use the AVO on the dc voltage range of course. Understood Rob. Quote Link to post Share on other sites
c.hydes Posted February 18, 2022 Report Share Posted February 18, 2022 53 minutes ago, c.hydes said: Thanks Rob, I will remeasure with the RC network firstly and if necessary see if it has the adjustment screw fitted. Colin. Hi Rob, what's the series diode for in the circuit, surely this will drop 0.7v on the charging cycle? Colin Quote Link to post Share on other sites
RobH Posted February 18, 2022 Report Share Posted February 18, 2022 Hmm - good point Colin I hadn't looked closely at that. The diode shouldn't be there. With that in circuit there is no discharge path and the voltage will just 'pump' towards the peak which isn't what you want to measure. The reading on the meter will take a few seconds to settle at the average. Quote Link to post Share on other sites
c.hydes Posted February 18, 2022 Report Share Posted February 18, 2022 5 minutes ago, RobH said: Hmm - good point Colin I hadn't looked closely at that. The diode shouldn't be there. With that in circuit there is no discharge path and the voltage will just 'pump' towards the peak which isn't what you want to measure. The reading on the meter will take a few seconds to settle at the average. Yeah diode not logical, for both reasons, so will leave out. Quote Link to post Share on other sites
c.hydes Posted February 18, 2022 Report Share Posted February 18, 2022 3 hours ago, c.hydes said: Yeah diode not logical, for both reasons, so will leave out. Just retested with the smoothing circuit (no series diode) Rob. 10K and 10uF still pulses, but with 100uF is fairly smooth with AVO or digital at about 8V dc. So assume that's why gauges read low? Colin. Quote Link to post Share on other sites
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