Harbinger One 2015 not working (LFO)

[Kardnez]

Hello,

I've finished building my Harbinger One (2015), but it doesn't work. The bulb glows continuously but quite dimly, and can only be adjusted with the Gain control. The Offset control has no effect on the bulb. The operating voltage is 18V. There's no signal coming from the circuit either, only in true bypass mode. I've checked the components without success and searched the board for solder bridges and cold solder joints. The Speed ��Pot is connected correctly. I've measured transistors Q11 and Q12, as well as capacitors C23, C24, and C25. When turned on, LED 1 flashes once.

The LFO isn't working, but as I said, there's no signal coming from the circuit either.

What could be the problem?

Thank you very much

Holger

[Kardnez]

Update:
I replaced Q11 and Q12 with 2N3904 transistors, and the LFO is now working. However, there is still no signal coming out of the circuit. The input signal is present at the base of Q1, but no signal is coming out of the collector/emitter. Q1 was also replaced with a 2N3904. The DC voltages in the preamplifier stage look good.
Does anyone have an idea?

Thx
Holger

[NorthCoast]

Can you post some pics?

What voltages are you getting on Q1?

[Kardnez]

Hi,

here are the voltages.

Q1
C 2V
B 1,32V
E 1,28V

Q2
C 5,42V
B 2V
E 1,45V

Q3
C 12,36V
B 5,42
E 4,84V

I use a 18V power supply.

Holger

[NorthCoast]

Hi Holger,

You mentioned you've replaced 3 transistors, what transistors did you have in there before?

Is it possible Q2 and Q3 need to be replaced?

It seems like every time you replace a transistor, there is an improvement.

[Kardnez]

Hello,

originally, Q2-Q13 were 2N5088 and Q1 was 2N5089. The LFO wasn't working, so I found a suggestion in older posts here on the forum to replace Q11 and Q12 with 2N3904s. This did the trick; the LFO now works. Since the input signal only goes as far as the base of Q1 and then stops, I also replaced Q1 with a 2N3904. Unfortunately, without success. I removed Q2 and tested it with a transistor tester; according to the tester, it's OK. I reinstalled it. I haven't replaced Q3 yet.

Could it be possible that several 2N5088s are faulty?

I can try replacing Q2 and Q3 with 2N3904s.

[NorthCoast]

Huh, I don't know.

Yeah, you could try replacing Q2 and Q3.

[Kardnez]

Hello,

I've had some partial success. After replacing Q2 and Q3 with 2N3904s, a signal (switch set to Chorus) is now present at the output.

Unfortunately, the vibe signal is quiet and distorted. I think I'll have to replace the remaining 2N5088s with 2N3904s as well.

[jimilee]

Is it safe to say you put the back cover on before you test it? I may or may not have made that mistake.


Sent from my iPhone using Tapatalk

[NorthCoast]

Assuming you put the back cover on... haha ...  yeah I think replacing the remaining 2N5088s with 2N3904s would be a good idea.

[Kardnez]

Hello,

Yes, I had the back cover on. 

It works now. After replacing Q4-Q10 with 2N3904s, everything is running smoothly. What I don't understand is why the Harbinger 1.5 and even 2.0 still use 2N5088s. Maybe I got a bad batch, but they were definitely the cause. According to the transistor tester, they're all fine. Annoying, because the device would have worked from the start...

Anyway, never mind, now I have a working device.

Thanks for your thoughts and contributions.

Holger

[jessenator]

Reading this makes me want to go back to my Harbinger 1.5... I wonder if my cheap 5088s are the problems. That poor thing has been in an esd bag for years now 

[NorthCoast]

Hello,

Yes, I had the back cover on. 

It works now. After replacing Q4-Q10 with 2N3904s, everything is running smoothly. What I don't understand is why the Harbinger 1.5 and even 2.0 still use 2N5088s. Maybe I got a bad batch, but they were definitely the cause. According to the transistor tester, they're all fine. Annoying, because the device would have worked from the start...

Anyway, never mind, now I have a working device.

Thanks for your thoughts and contributions.

Holger

That's great Holger!

Reading this makes me want to go back to my Harbinger 1.5... I wonder if my cheap 5088s are the problems. That poor thing has been in an esd bag for years now 

Give it a try, maybe we can help.

[jwin615]

3904s have a higer Vbesat and lower Vbeo. Maybe the small difference in B and E in Q1 and Q2 were not allowing the 5088s to conduct?