VOGONS


First post, by mongaccio

User metadata
Rank Newbie
Rank
Newbie

I have a problem with my p6bat.

The attachment IMG_20250808_094319875.jpg is no longer available

I tested it for a couple of hours,cpu fan spinning normally. After a reboot, fan stopped spinning. Fan Voltage drops from 12 to to 2 volts when a 3 pin fan is attached. Made a visual inspection of the board and i probably found the culprit,the cracked transistor q11(had 2 pins shorted)!.
it's output is directly wired to the fan + , and one of the gates is directly attached to the psu + (the collector maybe?), the other one is attached to another transistor (seems the control circuit)and is probably the base?

The attachment IMG_20250808_094428571_HDR.jpg is no longer available

Problem is... i've searched the code'h3nTG ' on the web and on code database, finding nothing. No dice with the motherboard schematics.

I'm quite sure it's a transistor(has 3 pins), but what if it's a regulator or a mosfet? I'm a bit lost.

In the meantime i've desoldered it, and in the worst case scenario i can bypass the trace and run the fans directly with 12v and no tachometer line (maybe putting a resistor to run 'em quieter at a lower voltage)

Reply 1 of 3, by shevalier

User metadata
Rank Oldbie
Rank
Oldbie

typical fan control of the those times.

PS
The PMBT2907A is prefer by power then MMBT3906
https://imrad.com.ua/userdata/modules/product … BT2907A_nxp.pdf

Aopen MX3S, PIII-S Tualatin 1133, Radeon 9800Pro@XT BIOS, Audigy 4 SB0610
JetWay K8T8AS, Athlon DH-E6 3000+, Radeon HD2600Pro AGP, Audigy 2 Value SB0400
Gigabyte Ga-k8n51gmf, Turion64 ML-30@2.2GHz , Radeon X800GTO PL16, Diamond monster sound MX300

Reply 2 of 3, by mongaccio

User metadata
Rank Newbie
Rank
Newbie
shevalier wrote on Today, 12:35:

typical fan control of the those times.
PS
The PMBT2907A is prefer by power

Well, thank you very much!

This is some useful info, the transistor in the schematic matches the wiring on my motherboard (except for the missing resistor between the mosfet and the transistor)

With this info i can try to replace it with more confidence, i'll try with a regular pnp and a more powerful switching transistor (if i can find it in my spare parts), i'll try it

Reply 3 of 3, by shevalier

User metadata
Rank Oldbie
Rank
Oldbie

If the transistor does not have a base resistor, it is better to use the circuit from the Radeon X800 on a mosfet.
It will be much more reliable.

https://www.alldatasheet.com/datasheet-pdf/do … Y/SI2301DS.html
Or something like P-channel, 20V, > 0.5 Amper, sot 23.
All other parameters are not critical at all.

Aopen MX3S, PIII-S Tualatin 1133, Radeon 9800Pro@XT BIOS, Audigy 4 SB0610
JetWay K8T8AS, Athlon DH-E6 3000+, Radeon HD2600Pro AGP, Audigy 2 Value SB0400
Gigabyte Ga-k8n51gmf, Turion64 ML-30@2.2GHz , Radeon X800GTO PL16, Diamond monster sound MX300