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You know best if you need to remove the board. I can’t advise on that because I don’t know the physical constrains/circumstances you’re dealing with, so do what you need to do. The board will need to be fully connected unless you’re able to power it and inject test tone on a workbench, and my...

That’s for you to decide. But first of all, remember, you don’t even know if the LC4966 is the problem. So first it would be good to learn if it is, and then decide if you want to replace them all. You should make your own decision. If it was me, if one has failed, and, knowing there is a...

I already answer your repeat question in my last post. Please read.

Word of advice: be careful about powering up with certain assemblies removed. I think it’s not likely an issue in the Series 30 tape machines, but I’ve had bad outcomes in other machines, namely the 388, powering the unit with one or more assemblies removed. We would all like to think the system...

Yes. I’ve seen a pattern of failures of the LC4966 in the 388 and the M-300 series consoles…enough that I think I purchased some at some point to have a stock of them here. There are several quad bilateral switch options in that package. The problem is all the other options, IIRC, have a maximum...

Oh okay. That’s all I needed to know. If you have audio in the headphones and activity on the meters you should have audio at the line outs. I just wasn’t clear on that.

But can you confirm audio passes to the outputs now after the work in the power supply PCB? Otherwise, if not, it seems to me nothing has changed.

Dude…okay…thanks for clarifying…so there is mechanical snapple crackle pop unrelated to the audio outputs…! That’s a bit freaky. So where are we at? You recapped the power supply PCB and replaced the bridge rectifier diodes for the +6V supply, and did you also replace D805 and D806? And you...

Awesome. Okay. So maybe you had a failed bridge diode, or even though the filter cap was measuring in spec as far as capacitance it was not performing correctly dynamically because some other aspect was out of spec. Is the snap crackle pop at all outputs or just the headphone output?

The most common cause of transport issues in the AG-440 series has to do with bad relays. The best recommendation is to replace all the relays plugged into the transport control box; “14-pin 24V ice cube relay”…just do a web search for that. These are very common…presently found in mechanisms...

Yes. Sorry about that. I updated the post. Yeah that’s essentially it. And it’s not just using the +6V rail as a messenger at power-up, but also power-down, because impulse voltage happens in both cases and could thump the outputs either way. It’s no different than my power conditioners I have...

Thanks. The 1N4006 parts are indeed overkill for D801~805, but there’s no harm in it. Use what you have for those parts. D806 is different. D806 provides for that reverse-flow of the timing circuit at power down immediately breaking the circuit to ground for the muting relays’ coils and...

I’m not sure what your numbers mean…590, 240, etc. Depending on the tester, diodes should read a given voltage in the forward direction and zero in the other. Regardless, it’s best to test diodes out of circuit. I would not be going hog wild on all your diodes. I recommended shotgunning the...

There are more things to test besides capacitance. ESR is another. But, look…those caps are over 40 years old. And these are not caps that were manufactured like some of the high-quality computer-grade caps that are found in the power supplies of like my Ampex and 3M machines that are...

Recapping typically only refers to the electrolytic caps; typically no need to replace any of the non-electrolytic caps unless there’s a known fault involving one. I’m not familiar with F&T caps. I use Nichicon, Panasonic, Vishay/Sprague, Cornell Dibiloer or Mallorey. 105C yes. On the diodes...

You can’t test caps in circuit.

I am not either. I consider myself an advanced hobbyist. I do my best not to get others in trouble. And FWIW, on your case, I’ve probably ready that segment of the Theory of Operation 4 times, and throughout our correspondence been in the schematics at least a dozen times. Notice it wasn’t until...

I would actually consider 6MOhm open circuit. That is very high resistance and the fact you have something measurable when the system is powered down is likely only because of some stray path to ground when components are not in their powered state. The bottom line is, after a few seconds, there...

Don’t strap pin 3 J171 to chassis ground…strap it to the power rail’s 0V reference on pin 2. The power mute timing circuit on the power supply PCB doesn’t “share the same rail” as the +6VDC lamp power rail per se, but, yes, there is association. As I stated earlier the timing circuit uses the...

You may or may not hear any mechanical noise from the muting relays. It depends on the relays. So I wouldn’t focus on that mechanical feedback. I don’t know what’s mounted. What happens if you ground J171 pin 3 and power up? Prepare your monitor system for a power thumb beforehand. Does audio...