Where can I find Peavey 87478 ICs for a Phasor circuit?

[QdB]

1978 Peavey Musician Mark III 400G (400b/g on power board) All working except phasor oscillation. The color control works, you can hear a shift in tone as it is turned. The Rate Control does not work.
I checked on similar posts regarding Peavey Phasors.
http://music-electronics-forum.com/t16596/#post135403
http://music-electronics-forum.com/t43929/
This seems to be a common issue in Peavey's of that era and it seems to always lead back to the 87478 IC. It also looks like that particular part and its replacement have gone obsolete and difficult to find. Does anyone here know of a reliable source for these parts?

EDIT: I did try to contact Peavey but no luck there.

[52 Bill]

1978 Peavey Musician Mark III 400G (400b/g on power board) All working except phasor oscillation. The color control works, you can hear a shift in tone as it is turned. The Rate Control does not work.
I checked on similar posts regarding Peavey Phasors.
http://music-electronics-forum.com/t16596/#post135403
http://music-electronics-forum.com/t43929/
This seems to be a common issue in Peavey's of that era and it seems to always lead back to the 87478 IC. It also looks like that particular part and its replacement have gone obsolete and difficult to find. Does anyone here know of a reliable source for these parts?

EDIT: I did try to contact Peavey but no luck there.

The generic number for that part is CA3094. Peavey used to make a small adapter board as a replacement for that chip, but it may be obsolete as well by now.

That chip is used in a lot of pedal phasers from that time period, and there may still be some out there at the pedal parts suppliers, like Small Bear Electronics.

[Enzo]

Peavey made an aadaptor board for the TL604, but I don't recall one for this chip. But me not recalling is not the same as them not making one.

This seems to be a common issue in Peavey's of that era and it seems to always lead back to the 87478 IC

It isn't that they commonly fail, it is more that people come to the internet WHEN they fail. The 87478 is just as reliable as all the other ICs.

I actually have several of them in stock, but they are not accessible easily. I will put them on my list of things to dig out next opportunity I get. Keep looking though.

If your channels both work, look at the plain channel. There is a 478 at the end of that channel. Steal that IC for now, and sub it into the rate circuit one by one. That will tell you it is the IC or not.

[g1]

So it's 3080 and not 3094?
As with any obsolete chips, beware of counterfeits from China.

[Enzo]

The two can SOMETIMES be used in place of each other, depends on how the circuit uses the output transistor in each.

[DrGonz78]

I have used Utsource on some obsolete items and they have not let me down yet.

https://www.utsource.net/itm/p/1882570.html

[52 Bill]

So it's 3080 and not 3094?
As with any obsolete chips, beware of counterfeits from China.

According to the Peavey cross reference, its a CA3094.

[QdB]

I have used Utsource on some obsolete items and they have not let me down yet.

https://www.utsource.net/itm/p/1882570.html

I'll check them out and report back.

from the site

Shipping:
Send to United States by Post
Goods will arrive in 15 to 20 working days

I'm in no hurry.

[Enzo]

Look at the data sheet for the 3080 and the 3094. If I recall, the difference is in the output transistor. There are SOME PV circuits using one where the other would also work. Occasionally you can take advantage of that.

[g1]

Seeing as they list over 30,000 in stock, I'm going to guess they're from China.
Perhaps they will work. If not, there are some NOS can style on ebay (RCA). You can bend the legs and make them work. There are also new cans ("Harris") coming out of China so watch out for those.

[drewl]

Is that the same switching IC used in the Marshall 2205/2210 ?

Edit: nevermind. That's a 3096, also discontinued.
Found a tube after making one of discrete parts for a rush job.

Happy hunting.

[QdB]

Alright. Got my chinese chips. (3094s, Not a snack food!)
Popped them in. Still no phaser. Not sure if it is the chips, or some other component.
I had also tried to swap u11 then u12 with u16, neither swap made a difference.
I clearly don't have enough experience to fully suss out the workings of that circuit, so I am fully open to any suggestions.

[Enzo]

Find a part of the amp that is working and uses the chip. Swap your new ones into THAT circuit. That tests the new chips, so you know if they are OK or not.

If they are OK, then first see if your LFO is working, it steps the bucket brigade along.

[QdB]

Find a part of the amp that is working and uses the chip. Swap your new ones into THAT circuit. That tests the new chips, so you know if they are OK or not.

I swapped the chinese 3094s into U4 (478 in the B channel [i think]). B channel works with them. After that, I swapped U6, U7, U8, and U9 into U4. They all work also. After that I swapped U10(604) for U2(604) didn't affect any change. Does U2 just turn on the channel led?

After that I put my meter on pin 6 of U12 and with the phaser switched out I got 5Vac and 0Vdc, with the phaser switched on and at various rate positions I got 5Vac and 0Vdc.

If I understand correctly, (which If I were a gambling man, I wouldn't bet on it), voltages from pin 6 should be sweeping? oscillating?

At any rate (see what I did there?), that is where I am so far in this adventure.

[Enzo]

Does U2 just turn on the channel led?

other way around, the LED circuit also turns the 604 side to side. TL604 is a dual switch. U2 and U14 are used to turn the preamp channels on and off with a footswitch. Just as the TL604 at the end of the reverb is its turn-off by footswitch.

U12 is the phase LFO (with U11). it is a low freq oscillator, yes. The LFO runs all the time, the phasor is switched in and out of the signal path. So turning phase on and off won't affect U12. Note that LFO runs through R64 to all the pins 5 in the bucket brigade of 478s. Got that LFO on each pin 5?

At the end of channel A is U17, which is a buffer to drive the bucket brigade. Got signal ther? With phasor on, look at the output of each 478 along the brigade. Pin 6 in each case. Is the audio signal moving along the chain?

Look at U9, see the little 2uf cap at the output, C41? Those are my favorite suspects in the amps of this era, they didn't age nicely. See if it is passing signal.