Recent content by alexhastings

Your pin 8 reading is low- it should be around 7.5-8V. have you checked the charging capacitor yet? If you monitor the pin as you turn on, you can watch the voltage rise as the cap charges up

Hi guys! Pin 7 will indeed have some measurable AC voltage- in both the original chip and the replacement, under normal operation, you should measure about 0.7VAC (from pin 7 to ground). it's clamped to that value by an internal diode, so it should be stable. So the original measurement looks good!

Hi @bbtv - the pins should correspond exactly to the original chip. If you're using the ebay kit you'll have to cut off a pin from the header to make it match exactly and fit in the footprint on the protection board. Go ahead and ask any questions you might have and I'll do my best to answer!

Awesome, this is a new unit to me regarding the PA3004 chip - glad it's working!

If you post the model you're working on, and the voltages (pin 7 should be an AC voltages - the rest are DC) on each pin we may be able to help you troubleshoot further!

Hello - I laid out the board, so I can confirm - the highlighted footprint is indeed Q7 - good luck!

I would say that Pin 4 voltage is definitely triggering the PA3004 to drop Pin 3 low and switch the relay off. What you are seeing on Pin 8 is the timing capacitor charging back up, since Pin 4 has gone back to 0V and all other inputs are good. When Pin 8 gets to 9-10V (cap is fully charged)...

Solely a design change in the graphics on the boards- the boards you had made should work totally fine!

I actually wanted to change the silk screen a little to pay tribute to Merlynski- I can work on it tonight!

We all miss Merlynski dearly - he will not be easily replaced! I'll give helping you a shot. It seems like your Q22 base voltage isn't right - it should be -0.6V. You should definitely double check if you have Q22 and Q20 installed correctly. If those look good, I would want to look at the...

Sigh, that's what I get for trying to do the voltage divider math on post it notes at work - you are correct on both accounts!

hehehe the "Top Secret" Pioneer sheet does have specs for Pin 4 - it says +-0.3V to trigger, and I was able to verify that on a working PA3004 chip. The substitute board has a slightly higher trip voltage - pin 4 will trip the circuit at about +-0.5V. Merlynski and I decided that it was an...

this has been gnawing at me for a couple weeks, so I looked at it again tonight. for the 980, it looks like there is a 75k->10k resistor divider from the active channel to the PA3004, so the voltage offset gets knocked down before it hits the chip. Using that voltage divider, -4V on the channel...

Glad you got it working! You asked about testing in place - I found that the DC offset was very difficult to test using the existing circuit. The only way I found to do it (I found this completely accidently) was with leaking new BJTs installed in my SA-7700 (Q19 and Q20 if you feel like pulling...

Aw man that's a huge bummer! RIP Steven!