Hello,

That model fans seems not to be available anymore.
It is not given in the SUNON datasheet as 3.4 Watt.
The KD2408PTS1-6A is 2.6 Watts.

Bertus

 

@bertus
I was going to ask if this is worth swapping out, but suppose it still works well so probably no point

 

If it's running at 39v but rated for 24v it's sure is a well made fan. I'd keep it.

 

If it's running at 39v but rated for 24v it's sure is a well made fan. I'd keep it.

 

Wonder if i have some dry joints around IC3, its only since i have been probing around that area the thermal L Has came on and the protect light is on now

 

It should not be possible to have 39 volts across the fan. From the wattage rating of the fan it should consume about 142 mA. That would mean that there would be 14.2 volts each dropped by R123 and R131. as we have 48 volts between +24 and -24 volt rails the fan should have a maximum of 48 - 28.4 - 19.6 volts across it.
Measure the voltage between collector and emitter of Q50, the voltages across R123 and R131. As something has changed (As the overtemp light is now on.) repeat the voltage measurements that you took in post #375 on the cathodes of D39 and D40.
Edit Are either LED 3 or LED 4 lit ? (overtemp indicators for each channel.) are the heatsinks hot ?
Les.

 

Measuring ripple:

You set the scope to AC coupling. The ripple will likely be <100mV p-p at a frequency of 2x he line frequency - e.g. 100 Hz. The +-15V supplies being OK, probably means ripple is OK.

==

You now have a fault. You can inspect/wiggle parts on the bad side and see if you get lucky or start actively troubleshooting.

You ave a good side to compare to.

D39 cathode = 14.78vdc
D40 cathode = --13.69vdc

Those measurements suggest a problem with the signs being different.

 

The readings in post #387 indicate the fault is related to the right hand channel.
What are the voltages on T14 and T16 with respect to T26 ?

Les.

 

I think i knew early on i was going to have a problem when i got here,
thats why i said i was concerened about the fan speed,
when i started this project the fan never spun up at all when i turned it on,
then something changed and it started working, when it did i noticed but had no idea why, And never chased the cause of this

 

The readings in post #387 indicate the fault is related to the right hand channel.

Why in post #385 is LED Thermal (L) lit?

 

Lots to digest here guys, i will have to re read the last few posts a few times and come back to you

 

Assuming things have not changed since post #385 and post #387. Then confirm that LED 3 (Thermal (l) is on and the voltage readings are
D39 cathode = 14.78vdc
D40 cathode = --13.69vdc
then measure the voltages on T13, T14, T15 and T16 with respect to T26.
Even if the conditions are not the same still report the readings and the state of LED 3 and 4

 

LED 3 L is still on, so is the overheat and protect LED on the front panel, right chanel still works and produces good audio
D30 cathode = 14.24vdc
D40 cathode = --12.58vdc
T13 = 0.508 vdc
T14 = 0.482 vdc
T15 = 0.433 vdc
T16 = 14.754 vdc

 

Check the voltage on both ends of R152, Q42 base and Q42 emitter with respect to T26.
I think there are two faults in this area.
Les.

 

R152 =14.74 both sides
Q42 B = 0.595 vdc
Q42 E = 0.000 vdc

 

I suspect you may have swapped the T15 and T16 values.

Guessing Q42 or Q16 is open or bad connection. Take a look at the B-E voltage readings of Q42 and Q16.
==
Suggest paralleling (in the same direction as the B-E junction) a diode between

the base of Q42 and ground(E) and
the base of Q16 and ground(E)

temporarily one at a time and see if the LED goes out. The appropriate side of R151 or r152 is more appropriate to use. There will be a time constant.

The R152 voltages suggest something wrong with Q42, but it doesnlt make sense with the Left channel over temp light being on. e.g. open.

There could be a schematic error.

Guessing Q42 or Q16 is open or bad connection. Take a look at the B-E voltage readings of Q42 and Q16. Use a voltmeter while the amp is on, not the transistor checker.

 

R152 =14.74 both sides
Q42 B = 0.595 vdc
Q42 E = 0.000 vdc

Considering that one side of R152 is Q42 base, what does that tell you?

14.74V = 0.595 Volts?

Nope.

There is a break between Q42b and R152. Anyway, Q42 has a break somewhere,

 

Fan comments: Back in the 1980s fan replacements were common in mininicomputers and part of the PM. They are impedance protected and thus can sustain an indefinite stall. The culprit was always dust. One particular brand could be disassembled and cleaned.

I never saw any bearing wear.

The fan should rotate effortlessly.

 

Re done the test in post #394,
There are no breaks between Q42B and R152,
R152 bottom = 14.730 vdc
R152 top = 14.729 vdc
Q42 B= 14.730
Q42 E = 0.000

 

I suspect you may have swapped the T15 and T16 values

I did not get T15 and T16 mixed up

Guessing Q42 or Q16 is open or bad connection. Take a look at the B-E voltage readings of Q42 and Q16.
==

Q42 B and E voltage = 14.750vdc
Q16 B and E voltage = 0.433 vdc

Suggest paralleling (in the same direction as the B-E junction) a diode between

the base of Q42 and ground(E) and
the base of Q16 and ground(E)

temporarily one at a time and see if the LED goes out. The appropriate side of R151 or r152 is more appropriate to use. There will be a time constant

Tried this but there was no change and the left temp LED stayed on

Also please remember Q7 bias regulator on the left chanel is NOT CURRENTLY FITTED !!