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Dynaco 416

F

firemedic08

New Member
Hey Everyone. So I finally got around to getting my dads Dynaco 416 with C100 cap bank and a PAT5 preamp out to start putting his stereo back together. They amp is paired with a set of Dahlquist DQ10's. I remember before my dad passed away 10 years ago he was having issues with the amp. So i plugged it in to try to troubleshoot the issue. At first the C100 was stuck on charging but I assumed that the caps needed to charge up so after about 15 minutes the power light lit up. After shutting it down and letting it sit the C100 powered up in about 10-15 seconds. I hooked up the speakers and only got sound on the right channel. Is there any particular place I should start to start the troubleshooting process? Thanks in advanced!!
 
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Start testing transistors and emitter resistors on the non working amplifier board. Once the problem is found there are update and repair kits available. As old as this amp is, the electrolytic caps should be replaced. There are cheap transistor testers that will tell you if they are shorted.
https://updatemydynaco.com/storeindex.html
 
Ok great. I was actually cleaning it up yesterday. My dad was a heavy smoker and the equipment was covered in smoke residue. I started my cleaning the heat sink and fan. After giving it outside a thorough cleaning I fired it back up and the left channel started to work. I think it is the left channel pot that was giving me the issue. I am going to take that apart and clean it. The levels are a little off. I have to run the right channel at 80% and the right at 100% so the channels have the same output. But I will also look at changing the caps as well.
 
Upon further testing both channels work perfectly when the level bypass is activated but when it is off the left channel is still off from the right significantly.
 
That bypass switch bypasses the controls. Like the filter controls, limiter,etc. Activating the switch connects your source directly to the driver board. Nothing wrong with that, except as stated the other controls are bypassed. So, it your getting less output from one channel when the bypass is switched off, then there is a problem somewhere in the controls. Maybe something as simple as a dirty gain control.
 
Lavane said:
That bypass switch bypasses the controls. Like the filter controls, limiter,etc. Activating the switch connects your source directly to the driver board. Nothing wrong with that, except as stated the other controls are bypassed. So, it your getting less output from one channel when the bypass is switched off, then there is a problem somewhere in the controls. Maybe something as simple as a dirty gain control.
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Going to get some cleaner and try that. I am hoping that is the only issue. Its just strange that my dad didn't figure that out. Is the CRC contact cleaner good to use?
 
I use several cleaners including CRC. I have CRC and Deoxit 5 at the moment. I use CRC a lot.
Did you try working all the other controls to see if any of the others made a difference?
And where do you have the limiter set? The manual says to set the Dynagaurd to 20 for normal operation.
 
i had a pat5 on the bench last week. all electrolytic caps where bad. I replaced a few caps in the power supply and line level boards just to get it working. I'd suggest going through the pre amp and expect you will need to replace a few caps.

Also know the PAT5 power switch only controls the convenience outlets. the pre is always powered up.
 
Lavane said:
I use several cleaners including CRC. I have CRC and Deoxit 5 at the moment. I use CRC a lot.
Did you try working all the other controls to see if any of the others made a difference?
And where do you have the limiter set? The manual says to set the Dynagaurd to 20 for normal operation.
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I have tried switching the DB dial and i have also played with the filters. As mentioned in the previous post everything sounds great and is basically balanced when the bypass is activated. But when the bypass is off the left channel is muuuuch lower than the right. I have the Dynagard set to 40 at the moment. TBH I thought that was some sort of thermal protection due to the hi temp light being above that dial. I really have no experience with this amp as my dad never let me touch it when i was a kid lol. So now I am trying to learn everything about it. But man does it sound amazing even on the crappy speakers I am using to test it out on. I'll upload a video to youtube later and post the link.....but you have to listen to the video on headphones. Computer or phone speakers do it no justice.
 
rickl said:
i had a pat5 on the bench last week. all electrolytic caps where bad. I replaced a few caps in the power supply and line level boards just to get it working. I'd suggest going through the pre amp and expect you will need to replace a few caps.

Also know the PAT5 power switch only controls the convenience outlets. the pre is always powered up.
Click to expand...

Great advice but at the moment I am not thinking its the preamp.....but i could be wrong. I did also notice that the preamp works when the power on it is off...I thought it was another issue I would have to address.
 
The Dynagaurd is a limiter circuit. The more it's adjusted to reduce power output, the harder it's running that circuit. I have a Sony amp with basically the same thing. The adjustments are 1/4, 1/2, and Full power. With the Sony its best to run it at Full. It's something that just isn't really needed as long g as you don't push your speakers into clipping. I run 100+ wpc amps into 25 to 70 watt speakers all the time without any problems.
 
Lavane said:
The Dynagaurd is a limiter circuit. The more it's adjusted to reduce power output, the harder it's running that circuit. I have a Sony amp with basically the same thing. The adjustments are 1/4, 1/2, and Full power. With the Sony its best to run it at Full. It's something that just isn't really needed as long g as you don't push your speakers into clipping. I run 100+ wpc amps into 25 to 70 watt speakers all the time without any problems.
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Ahh. Ok. That’s what I thought it was. So what is the DB dial?
 
firemedic08 said:
AhhOk. That’s what I thought it was. So what is the DB dial?
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That's the LED meter sensitivity adjustment. If listening at lower levels, it's adjustable so more of the LED's will light up. It's more of a gimmick, or for eye candy. Some stand alone power meters have a switch to switch between 1 watt, 10 watts, 100 watts, etc. You just don't want it set to a lower level setting when cranking up the volume. My Marantz power amp has meters. It doesn't move much at all unless you turn the volume up pretty high. It doesn't have a sensitivity switch.
 
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