I understand some will find it sacrilegious but I’ve been trying to bring bac from the dead this old time favorite, Philips AG 9016. I bought it knowing Someone else had been into it and seeing the electrolytic caps had popped out their internals. I replaced the electrolytic caps and retrofitted RCAs to it, even got it up and running with decent voltages and new tubes… but after a minute or two both channels fade out, then back in, then out…
I then changed the rectifier but to no avail. ‘Any ideas of what to try next? 🧐
I then changed the rectifier but to no avail. ‘Any ideas of what to try next? 🧐
Check the heaters - only thing I could think of that could make it fade in and out. Bad connection somewhere in the heater chain.
Motorboating as capacitors in the signal path and power supply have been replaced with higher values then specified?
A side question: This is an amplifier with a pair of EL86's in totem pole OTL configuration?
Best regards!
Best regards!
It should be with EL95 (2 watt amp)
https://www.lencoheaven.net/forum/index.php?PHPSESSID=k6p5c0jv7113t4nol3f0lnein2&topic=4689.30
https://www.lencoheaven.net/forum/index.php?PHPSESSID=k6p5c0jv7113t4nol3f0lnein2&topic=4689.30
Are you able to monitor B+ and heater voltages while it is running? I had an issue with an amp I made and it was a loose connection in a screw terminal. Maybe you have a bad solder joint somewhere.
The fact that it is both channels hopefully limits the issue to the power supply. Did you change the selenium rectifier? Have you tried tapping around with a plastic rod?
The fact that it is both channels hopefully limits the issue to the power supply. Did you change the selenium rectifier? Have you tried tapping around with a plastic rod?
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Yes, I have monitored both the transformer at the high voltage ac and 6.3vac. the high VAC is a steady 215 but drops to 188 and wink-out and the 6.3vac drops to 6.0. The cycles are pretty even at 5 seconds on and 5 seconds off, always with the right channel pooping out a half second ahead of the left. I have installed a new bridge rectifier.
I don't know what you mean by tapping around... I have examined all visible connection and they seem fine. The wiring is really skinny, maybe 28 or 30 ga in most spots but its hurried deep in globs of solder, 1963 style.
What DOES this kind of thing? The cyclic nature of it is baffling
I don't know what you mean by tapping around... I have examined all visible connection and they seem fine. The wiring is really skinny, maybe 28 or 30 ga in most spots but its hurried deep in globs of solder, 1963 style.
What DOES this kind of thing? The cyclic nature of it is baffling
Is it stable or not?
looks to me it is motorboating still.... Nothing strange here.
In contrast to the AG 9015/18 I don't know the AG 9016. But I concur with the motorboating cause.
Best regards!
Best regards!
I’m not sure I understand motorboating, I thought it was a fast oscillation due to a bad capacitor. This is a power drain in a slow 5 second period.
Most of the caps left on the board are ceramic type, not prone to failure. Four are of a type I’ve not seen before, one pair a dirty yellow blob but with value markings two others dirty yellow with painted strips like the ceramic ones. Am I down to just replacing every cap Or does it make sense to sell it for parts; the idea was to experience a vintage Philips amp, the further I get from original design the smaller my motivation to save it.
Most of the caps left on the board are ceramic type, not prone to failure. Four are of a type I’ve not seen before, one pair a dirty yellow blob but with value markings two others dirty yellow with painted strips like the ceramic ones. Am I down to just replacing every cap Or does it make sense to sell it for parts; the idea was to experience a vintage Philips amp, the further I get from original design the smaller my motivation to save it.
It can be a very slow oscillation as well as you are experiencing right now. It is a nice thing you have this as you can learn from it. The sound of this amp is really nice in the mid range (voices) but do not expect any low frequencies from it.
AIUI motorboating is normally occurring when the supply is loaded, and generally linked to bad decoupling capacitors from the power supply in an amplifier that was working fine before. Did you replace with the original value electrolytics? Maybe worth a try with no tubes to see if there is a power fluctuation then?
Some photos could be helpful.
Some photos could be helpful.
Thanks guys, I’ll post some pictures as well as some info/ voltages.
just to set the stage again, bought the unit not working yet fussed with, I replaced the electrolytics with close match and the rectifier. I’ve cleaned and inspected it and can get sound out of it but there must be a cyclic drain on the power transformer as it (5s) cycles between 215 and 188VAC. R1 gets pretty hot!
just to set the stage again, bought the unit not working yet fussed with, I replaced the electrolytics with close match and the rectifier. I’ve cleaned and inspected it and can get sound out of it but there must be a cyclic drain on the power transformer as it (5s) cycles between 215 and 188VAC. R1 gets pretty hot!
You could remove the tubes of 1 channel and check, then swap the tubes to the other chanel to see if it is related to one of the channels . In case it only shows when both channels are working it could be the output tubes as these will draw grid current over time. Then these need to be replaced.
