Harbinger 1.5- Signal Present When Engaged, No modulation

[Pauleo1214]

Good evening,

This may be a very stupid post. I have some LT1054 IC chips on order but my impatience got the better of me. I used an SPCA1044 and jumpered pins 1 and 8.

The board fired up fine. The bypass signal is working and I do get signal when the effectis engaged. I don't get any vibrato modulation however. The lamp lights up pretty well when the gain trim control is turned up almost all the way. It does fade in and out like it should when the speed control is adjusted though this is faint. The offset trim pot seems to have no effect.

Barring that IC1 is not the proper part, is it possible anybody else sees something obviously wrong with my board?

[jimilee]

Is it safe to assume you're testing it in the dark or with the lamp and LDRs covered up?


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[Pauleo1214]

Thank you for your reply. Yes, the PCB was tested in the dark and with a bottle cap covered in painter's tape and marked black with a sharpee.  Putting on the cap makes no difference I'm afraid.

[Cybercow]

Good evening,

This may be a very stupid post. I have some LT1054 IC chips on order but my impatience got the better of me. I used an SPCA1044 and jumpered pins 1 and 8.

The board fired up fine. The bypass signal is working and I do get signal when the effectis engaged. I don't get any vibrato modulation however. The lamp lights up pretty well when the gain trim control is turned up almost all the way. It does fade in and out like it should when the speed control is adjusted though this is faint. The offset trim pot seems to have no effect.

Barring that IC1 is not the proper part, is it possible anybody else sees something obviously wrong with my board?

If the lamp is glowing and dimming accordingly, then the chargepump may not be the issue. I'd check all of those socketed transistors and ensure they are all seated firmly with no wiggling or looseness. When I socket TO-92 BJTs, I always slightly 'wrinkle' the ends of the pins to ensure they seat firmly.

[Pauleo1214]

Hey there Cybercow, good to see you on the Madbean forums as well.

Unfortunately, firmly seating the transistors had no effect I'm afraid. The lamp does work and dim (very slightly) only when the gain trim pot is cranked all the way up which the user guide states to be wary of so as not to blow the lamp.

[Cybercow]

Hey there Cybercow, good to see you on the Madbean forums as well.

Unfortunately, firmly seating the transistors had no effect I'm afraid. The lamp does work and dim (very slightly) only when the gain trim pot is cranked all the way up which the user guide states to be wary of so as not to blow the lamp.

OK, it sounds like the lamp voltage is insufficient to me. So that 1044 may not be providing enough output to properly drive the LFO and lamp sections. I'd wait for the correct LT1054 charge pumps to arrive.

[Pauleo1214]

Had a first shipment of LT1054s arrive (from a seller on Amazon). I removed the jumper between legs 1 and 8 but still the same issue.

I have another batch from Mouser on order coming soon.

[Cybercow]

Had a first shipment of LT1054s arrive (from a seller on Amazon). I removed the jumper between legs 1 and 8 but still the same issue.

I have another batch from Mouser on order coming soon.

Did you check to see if the 15v is fluctuating with the Speed pot setting changes? IF it does not, then something may be wrong with the LFO section.

[Pauleo1214]

Let me look up the values and other voltages; I'll report my findings here.