Xtrons TD716G. Fault, or me being thick?!! - Page 4

charliedingo · 14th February 2010, 12:11

Quote:

Originally Posted by grahamts

If you are suffering memory loss caused by momentary voltage drop, then the mod above should help. However it won't help if the cranking goes on for too long, the cap will only hold the voltage up for a very short time. The larger value cap that you use the longer the voltage will be held to the higher value, (in practical terms, if you think of it as a battery with a very, very limited capacity then you get the general idea).
Looking at the range in Maplins, something like KQ68Y which is a 47uF - 35V electrolytic should do the job and for a diode the 1N5400 should be more than adequate.
I realise that I said 4.7uF originally, but 47 is 10 times bigger and bigger is definitely better in this case. They also do a 100uF which would be fine as well. If these don't, then just use a bigger value from another range.
It really depends what sort of voltage drop you are getting and for how long,
Graham.

hi, sorry i don't actually have a rover, i just joined to help solve this xtrons memory loss thing.
i've got the td712g model in a ford escort diesel.

in my case, there is about 2.5 - 3 volt drop when cranking the engine and it will take a couple of seconds in the cold weather.

i tried putting a 100uF 16v capacitor in but had virtually no effect.
is it the value of F that needs to increase or the working voltage?

i was reading up about using capacitors to keep the voltage up but it's looking like you'd need one of them "power caps" like they use for power amplifiers where require sudden rush of high power.
they're rated at 1 Farad - probably over kill for what we need it for.
or is there a place to get an uninteruptable power supply like they use for computers to keep the power on in power cuts but a 12v dc version?

them power caps are a bit pricy to fix a problem that's more of an irritation than a fault

grahamts · 14th February 2010, 20:03

Hi Charlie(?)
it's is the capacitance that matters, not the voltage, which only needs to be greater than the operating voltage.
The greater the capacitance, the more storage potential, similar to AHr rating of car batteries, however even with very large farad ratings the current output is very limited. If you didn't use a blocking diode then the cap would discharge instantly toward the car battery when the starter is turned.
You need to supply current to the radio and not to the starter, hence the diode. Check the diagramn on the previous page.
Hope that helps, Graham.

charliedingo · 15th February 2010, 21:21

cheers, might have another go at it, think i had it wired correct but now i'm not so sure - i too suffer occasional memory loss when i go to sleep!

charlie

14th February 2010, 20:03	#32
grahamts Regular poster MG ZT Tourer Join Date: Jan 2010 Location: Chelmsford, Posts: 31 Thanks: 0 Thanked 0 Times in 0 Posts	Hi Charlie(?) it's is the capacitance that matters, not the voltage, which only needs to be greater than the operating voltage. The greater the capacitance, the more storage potential, similar to AHr rating of car batteries, however even with very large farad ratings the current output is very limited. If you didn't use a blocking diode then the cap would discharge instantly toward the car battery when the starter is turned. You need to supply current to the radio and not to the starter, hence the diode. Check the diagramn on the previous page. Hope that helps, Graham. Last edited by grahamts; 14th February 2010 at 20:06..

15th February 2010, 21:21	#33
charliedingo Newbie none at the moment Join Date: Feb 2010 Posts: 2 Thanks: 0 Thanked 0 Times in 0 Posts	cheers, might have another go at it, think i had it wired correct but now i'm not so sure - i too suffer occasional memory loss when i go to sleep! charlie