Troubleshooting vintage Phase 90

[sonnyboy27]

A buddy of mine brought me a vintage phase 90 (6 single opamp version). I passes signal just fine but the phase signal gives me nothing. I've checked all of the ICs and they each are getting powered properly (9V on pin 7 and 0V on pin 4). I pulled out the audio probe and I noticed that the signal gets attenuated after the first capacitor and then comes out of the input buffer incredibly weak. From their I think the simple filtering in the rest of the audio path kills the signal off. Any phaser folks had experience with this?
I'm getting the appropriate 5.1V off of the Vref so I don't think that's an issue. I've been using the Electrosmash phase 90 analysis page to help me sort through the signal path.

[sonnyboy27]

Personal Update: Looks like the caps in the signal path may have drifted so far out of spec that they're filtering out the signal entirely.

[mgalicki]

I have a diy phaser 90 build that only sounds in the off position?
I used the Audio probe & I get a phased signal from the left side of the board, nothing passes by the green line.. R3, 4, 5, 6, & Q1, 2, 3, &4.
See the pic attached.
Any ideas? 

[jimilee]

Got pics of your build (both sides) along with voltages?


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[mgalicki]

As far as voltages, I am new to DIY builds so  I need a description of how to do voltages. EX: Do I ground to box & with unit in the on position, touch each component on the board to get the DC voltage reading? Thank you for your assistance. 

[jimilee]

Did it work before and then not work? Did you try turning the trimmer in mm increments? Did you check to make sure all of the parts are correct and have you reflowed all of the solder joints?  Sorry for all of the questions, it's a process starting with the above.

Ground the DMM probe to the main ground, the red probe will check each leg of the ICs and transistors.


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[Govmnt_Lacky]

Some of those solder points look highly suspect. You may want to clean that off with some alcohol and a brush and re-flow. In your pic, the lower right corner.... Pin 6 of that Op Amp looks bad 

[mgalicki]

Thanks, Jimilee & Govmnt_Lacky.
I will clean the rear of the board, re-tin the joints & then do the readings, Greatly appreciated! I'll get back to you later.

[mgalicki]

An update, Jimilee, after I first finished the build it did work, but only in the on position, I got a new push-button from the supplier of the kit for free because he said I was probably too heavy with the heat & melted it. After installing the new switch was when I got the results I originally posted above.  I have cleaned & resoldered all the joints, but still have the same results as above. I am now doing the voltage readings & will post them soon.

[jimilee]

Looks like there a missed solder joint on the bottom right.


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[mgalicki]

The open solder joint is for the jumper to use as a script model. Attached are the voltage readings and a copy of the board labels.

[jimilee]

Are both of these spots not supposed to be soldered?


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[mgalicki]

I see these 2 spots not soldered, I will ask the site  I bought it from & get back to you.
(It's actually these 2 spots, the lower left one in your pic is soldered.)
Thanks.

[Govmnt_Lacky]

I see these 2 spots not soldered, I will ask the site  I bought it from & get back to you.
Thanks.

Both of those solder points are legs from IC chips. They need to be soldered properly. Those were the points I mentioned in my previous post.

[mgalicki]

All IC chip solder joints have been soldered. There are 2 large unsoldered holes in the board I am asking the seller about.