Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

[labello]

Hi guys a friend of mine give me this old counter it's for Honda XL 600 LM 1985-1989 PD04.
He opened it and found a resistor that was blown up. Then he lost it. I knowing it's not easy to fix it, but I just guess (maybe we can) thank you so much

[stj]

Re: Resistor blown up and losted

9ohms or 39ohms
remove it to test it - then test that zener diode thats probably shorted.

[eccerr0r]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

R2?

That's going to be quite hard to figure out what it was, I was wondering how to derive 9Ω or 39Ω from a missing resistor... probably will need to locate an identical board or do a complete reverse engineer of the board and where each wire connects ...

[stj]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

i missed that, was looking at the discoloured one.
lets see the track-side to see what it does

2 ceramics, 1 tantalum, 2 diodes and a chip to test too - i doubt that resistor killed itself anymore than epstein did

[redwire]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

What is the IC's part number? Is this a tachometer?

[labello]

Re: Resistor blown up and losted

9ohms or 39ohms
remove it to test it - then test that zener diode thats probably shorted.

Hi thanks for your reply, but on the mark R2 it's empty I mean it was a resistor there but it losted. It remain a color like roasted.

[labello]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

What is the IC's part number? Is this a tachometer?

Hello it's a tacho rmp the part number of ICI is this on the picture. I hope to clean it good enough. Thank you for your help 🙏

[redwire]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

Toshiba T2295A IC is used in several tachometers for frequency to voltage converter. So the circuit can be figured out. Schematic is from a GB250? I could not find the IC datasheet.

Can you give a picture of the other side of the board.

There's no reason for any resistor to burn up (other than the 39Ω is just for IC power/feed for zener diode ZD1).

I think water might have got in and the resistor R2 arced or carbon-tracked on the board? The ignition coil input is high voltage, >400V spikes.
If the burnt resistor goes to the trimpot then it is 680Ω.
It might have damaged the IC. This might cook the 39Ω as well then if the IC is shorted.

[labello]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

Toshiba T2295A IC is used in several tachometers for frequency to voltage converter. So the circuit can be figured out. Schematic is from a GB250? I could not find the IC datasheet.

Can you give a picture of the other side of the board.

There's no reason for any resistor to burn up (other than the 39Ω is just for IC power/feed for zener diode ZD1).

I think water might have got in and the resistor R2 arced or carbon-tracked on the board? The ignition coil input is high voltage, >400V spikes.
If the burnt resistor goes to the trimpot then it is 680Ω.
It might have damaged the IC. This might cook the 39Ω as well then if the IC is shorted.

Hi thanks for your reply. I asked him, and he told me it was his mistake because he still restored the motorbike, and some wire about cabling was not connected to the ground on the chassis. So I look something smoking and turn everything off but unfortunately the resistor on tacho blown up. Now I don't know if the ICI is still good or it broken also

[labello]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

Toshiba T2295A IC is used in several tachometers for frequency to voltage converter. So the circuit can be figured out. Schematic is from a GB250? I could not find the IC datasheet.

Can you give a picture of the other side of the board.

There's no reason for any resistor to burn up (other than the 39Ω is just for IC power/feed for zener diode ZD1).

I think water might have got in and the resistor R2 arced or carbon-tracked on the board? The ignition coil input is high voltage, >400V spikes.
If the burnt resistor goes to the trimpot then it is 680Ω.
It might have damaged the IC. This might cook the 39Ω as well then if the IC is shorted.

Sorry i forgot to say thank you for the schematic 👍

[redwire]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

Can you give a picture of the other side of the board.

[labello]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

Can you give a picture of the other side of the board.

Sure... Here you are

[petehall347]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

looks to me like it got powered backwards and the diode did its thing and blew the fuse .

[redwire]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

The tach has reverse-polarity protection with D1. +12V is the black wire though... so I could see that mistake when running it on the bench.
You can't damage it connecting it up wrong. I drew the schematic.
It could be a shorted capacitor like C2 or C3. For the age of the tach, I would replace the 4 caps.
The burnt resistor is R2 is possibly (based on G250 schematic) 680Ω and worst case is 0.3W, it would not burn if the tach was connected wrong. You can put in a new resistor and power it up but it's a bit lower value but still would not burn so bad? Or the tech did something weird power it over 20V.

The IC is rare and the chinese offerings are apparently no good.

[labello]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

The tach has reverse-polarity protection with D1. +12V is the black wire though... so I could see that mistake when running it on the bench.
You can't damage it connecting it up wrong. I drew the schematic.
It could be a shorted capacitor like C2 or C3. For the age of the tach, I would replace the 4 caps.
The burnt resistor is R2 is possibly (based on G250 schematic) 680Ω and worst case is 0.3W, it would not burn if the tach was connected wrong. You can put in a new resistor and power it up but it's a bit lower value but still would not burn so bad? Or the tech did something weird power it over 20V.

The IC is rare and the chinese offerings are apparently no good.

Thank for your explanation, well I'm going to put the R2 resistor and we'll see what happens

[labello]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

Redwire you was right! The bolt capacitor are almost gone the c2 has very high esr so I thought it is shorted, the low capacitor in the c3 side give me strange voltage lower than 22uf and esr is a bit higher so I will replace all of them. It could be difficult to find this one. I never see someone like this one

[lotas]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

This capacitor is tantalum.

[stj]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

224 = 0.22uf, i would use a 220nf 63v polyester film cap

[labello]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

224 = 0.22uf, i would use a 220nf 63v polyester film cap

Hey thanks. The capacitor meter shows me 0.16 uf with a high esr. 220nf 63v are you sure? The motorbike is running just 12v

[redwire]

Re: Honda XL 600 LM 1985-1989 PD04,Resistor blown up and losted

Here is the Honda XL600 tach schematic I drew. It's hard with no IC datasheet or missing some part values. The 470uF 6V part usually fails and gives low or erratic readings or no reading. Check the other two electrolytics as well.
Polyester film caps come in 50V, 63V at the lowest. So a 0.22uF 63V MKT is OK to replace the tantalum part.

Toshiba F/V IC is used in many Japanese tachometers in cars, motorcycles, mopeds etc.
Maybe look at Honda CX500, Spree, Flush and Elite 50 etc. or Yamaha Virago.

T2295A IC a little bit similar to T2685A used in Toyota 4AGE MR2, Pontiac Firebird, Fiero tach. or TA8029S.