Phonic Powerpod 1860 II powered mixer - schematics or PT voltages needed

[Mick Bailey]

I need the voltages for CNP1 which is the main connector from the toroidal PT secondary to the power amp PCB. The PT primary is shorted internally, with no other signs of damage to the rest of the equipment. I have a transformer which may substitute, but need to be sure of the voltages and connections. Any assistance appreciated.

[Jazz P Bass]

Take a look at the high voltage filter capacitors.
What is the voltage rating?

[Mick Bailey]

100v. I'm guessing the amp is running 50v rails to give 300w into 4 ohms per channel. It just crossed my mind to see if any of the other primary tappings still work (say, 100v) to run it up no-load on the variac. The secondary has 8 connections arranged -Vx/-Vy/0v/+Vy/+Vx and -V/0v/+V (op amp supplies, assuming -15v/0/+15v DC resulting), if you see what I mean.

[Mick Bailey]

As soon as my Jackass Ears had sprouted I realised.......

Anyhow, it's shorted right out.

[doctor]

As soon as my Jackass Ears had sprouted I realised.......

Anyhow, it's shorted right out.

Here are the 1082 power amp and power supply schematics.
The 1860II model has the same.

[Mick Bailey]

That's fantastic. The main supply rails are higher than I'd thought - I ended up with thinking maybe towards 60v rather than the 50v I'd originally guessed, to allow for the amp not swinging rail-to-rail. Clearly still not high enough. The transformer I have won't work, so I've asked the UK Phonic distributor for a price on an original component.

Really appreciated.

[J M Fahey]

1) thanks doctor

2) your transformer is not shorted but open.
It has a thermal fuse embedded in the winding which opened during some overheating.
If the job is for a paying customer, by all means get the original replacement and avoid liability issues, but if it's for personal use, you might try to replace the original fuse and check whether it works.
Of course, if it sizzles, bubbles or smokes, junk it at once.

That said, the schematic seems to imply an option, but you must check it's so.
The thermal fuse is shown in series with the "0 VAC" wire (red in the schematic, don't know what the actual wire color is) but they also draw *another* "mystery wire" , which bypasses it.



***Maybe*** it's an option so under some circunstances some service people, if the original part is unavailable or shipping is troublesome , can "repair" it and pull a pesky customer off their back.
Just guessing here.

So have a good close look at the primary wires (not the ones in the PCB connector); if you find an unused wire, check that it has continuity across the now open winding.

[g1]

That said, the schematic seems to imply an option, but you must check it's so.
The thermal fuse is shown in series with the "0 VAC" wire (red in the schematic, don't know what the actual wire color is) but they also draw *another* "mystery wire" , which bypasses it.

[ATTACH=CONFIG]22885[/ATTACH]

***Maybe*** it's an option so under some circunstances some service people, if the original part is unavailable or shipping is troublesome , can "repair" it and pull a pesky customer off their back.
Just guessing here.

I'm wondering if the "mystery wire" is used when they wire it up for 120V operation. If wired for 120V the thermal wouldn't be much use there.

[Mick Bailey]

My ring tester shows it as a shorted. It's also drawing heavy current with the secondary disconnected and a 150w bulb limiter glows at full brightness. The transformer blows the 8A fuse when connected directly to the supply. I checked the secondary connector for shorts between pins just in case. The unused (brown) wire shows continuity across the thermal fuse to the 0 VAC wire.

I can't recall seeing a mains transformer in audio gear totally shorted. High current usually means open windings, though a shorted turn is a possibility and may be causing exceptionally high current draw. The mechanics of the start/end of the windings would suggest to me that a total short across the supply is unlikely. It also suggests that I'm overlooking something.