Yamaha D1500 delay help!

[MagnetoSound]

I've got an old Yammy D1500 on the bench with clock (sub-harmonics, I guess) bleeding through at the O/P. Nasty, jagged buzz.*

Can't see any way to null it, no trimmers except CLOCK (freq) and GAIN.

If anyone has a circuit diagram or has cured this in the past I would be grateful for any help.

Thanks.


(*this is not an album by Alanis Morissette)

 

[harleyb]

I have a schematic on paper but it's the huge foldout type and won't fit into my scanner. Any questions I can answer from the schematic?

 

[MagnetoSound]

Hi harleyb, thanks for chiming in, and welcome! ...

Can you see any obvious filtering that may have decayed with time - electro's or other caps on the clock supply line?

I guess I'm gonna recap the PSU anyway, but any other pointers would be useful.

Thanks.

 

[gyraf]

too-large-to-scan-schematics wants to hang on a wall - in good light - while being photographed by a digital camera..

Jakob E.

 

[harleyb]

Took some pix but details not legible. email me at [email protected] and I'll send'em to you. I can't really give pointers because I'm not sure what the problem looks like. Clocks usually don't have any filtering. I can tell you that this generation of d-to-a conversion always includes an analog LPF to filter out the clock/sampling noise and this is an area of high failure rate. (IC's 112, 113, and 114 in your case). I also noticed that this unit has several switch ic's (119-123, 130-133) and these also have a high failure rate. Does the PCB have schematic reference numbers enabling you to identify the above IC's? If you have a counter connect it to TP158 and adjust VR104 to acheive 512KHz. (+/- 2.5KHz). Is your audio clean at TP111? (thats the input to the a-to-d convertor). Let me know if I can help further.

 

[MagnetoSound]

Thanks Harley!

Email sent.

 

[MagnetoSound]

Harley, pics are as you say not really legible, but ...

Does the PCB have schematic reference numbers enabling you to identify the above IC's?

Yes.

If you have a counter connect it to TP158 and adjust VR104 to acheive 512KHz. (+/- 2.5KHz). Is your audio clean at TP111? (thats the input to the a-to-d convertor). Let me know if I can help further.

I could use some help identifying these TP's ... can't see any pins sticking up, nor any screening indicating where these points are. Maybe it's my eyesight failing ...

The noise does indeed seem to be on the A/D side, flipping the 'TEST' switch near to that LPF circuit you mentioned changes the timbre of the bleed somewhat, and it's clearly before the delay network as the sound changes after a few milliseconds depending on the delay time set. Can you tell me what the TEST switch does?

Thanks again.

 

[Aeres Custom]

I have a schematic on paper but it's the huge foldout type and won't fit into my scanner. Any questions I can answer from the schematic?

Hi harley,
please send me the schematic yamaha d1500,,
[email protected]
thank you