Assist With AMP 197-20 Please

[Hi-Fi-Mogul]

I looked at several explanations, and they all are
the same as Uncle Doug's.

Here's a succinct one regarding what I think is our interest:

"Negative feedback is taking some of the output of the power amp, inverting its phase, and feeding it back into the input. This has the effect of removing or cancelling out “errors” produced by the power amp.

Increasing negative feedback will reduce distortion, flatten the frequency response, and improve damping factor, or the ability to of the power amp to accurately control the motion of the speaker. For most hi-fi applications, these are all good outcomes."

[Hi-Fi-Mogul]

Last night I replaced the 5 caps in the chassis.

They were all mounted on the underside of the
terminal strips
I took my time getting the leads measured and
soldering them in carefully.

Today to start looking at the e-lytic capacitor
replacements leads' positioning and hole
drilling.

There is an open mounting lug eye from the cap
can that I can use for the new caps' negative
lead.
I will have to solder a small length of extra
wire to the caps' neg lead to reach the lug.

[William]

Nice work, Mr. Mogul. The bottom side reminds me of the amp in my Columbia/Magnavox.

Bill

[Hi-Fi-Mogul]

Today I finished installing the new e-lytic filter caps and
the e-lytic cathode bypass cap.

Yesterday, with very low humidity and reasonable temps,
I went over the Aristocrat cabinet with 0000 steel wool and
Re-Stor-A-Finish mahogany.

Lot of flea-bites disappeared, and overall looks nice.

I'll go over the electronics work tomorrow, and if all checks
good, then I have the Collaro changer to do.

[William]

I just took a quick look back in your thread to refresh my memory and I do not see a mention of the changer. If I may, which Collaro changer does this unit have?

Bill

[Hi-Fi-Mogul]

Bill,

The Collaro is an F200-C.

[William]

Thanks, Mr. Mogul.

[Hi-Fi-Mogul]

Amp re-cap was successful on testing.

Now I'm making headway in the dis-assembly and cleaning
of the F200C Collaro record changer.

One design flaw (for service at least) is that the tonearm
wires go through a hole in the sub-plate housing.

Due to the nature of the different muting system on this
changer, I did not want to unsolder the tonearm leads.

It just takes some careful moving around of the loose tonearm
and changer base/sub-plate when you start the dis-assembly.

Motor is cleaned and lubed. Rotor did not spin well prior to
service, but now spins like a top.

Controls' linkages are all cleaned.

Sub-plate assembly left to clean/lube manana.

[William]

This changer looks very similar to the Collaro 456. If I might ask, Mr. Mogul, what are the differences between the two that you have noticed?

Bill

[Hi-Fi-Mogul]

This changer looks very similar to the Collaro 456. If I might ask, Mr. Mogul, what are the differences between the two that you have noticed? Bill

The Collaro 456 has a completely different cycling mechanism, full
of nefarious linkages. [ : )

I tried once to get a 456 to work, and I'll never work on one again.
I replaced it with a 600 Micromatic, much nicer overall in looks
and function.

[William]

I feel the same about the 456, pain in the butt to work on. I know the 600 series is the newest series, between the 456, F200C, and the 600. Is that the order in which Collaro made those models, or was the 456 and F200C made at the same time just at different pricing levels? The F200C and the 456 look the same on the top side.

Bill

[Hi-Fi-Mogul]

I cleaned and re-assembled the F200C changer sub-plate
mechanism, and installed the motor.

All cycling functions are good.
The original idler and drive wheels will be
sent to Gary at V of Music for replacement.

One bump in the road is that the On/Off/REJ knob's
internal metal support is missing.
So, it will slip when engaged, and not activate cycle.

I had a 33/45/78 short height speed selector knob from
a Collaro parts unit, which will work instead.

The owners will be shown to engage the cycle by
turning that knob CCW.

Not aesthetic, but functional is good.

The original Sonotone 8-T stereo cart has some
wiring issues in the tonearm leads that will be fixed.

But, good news is that both channels work and
MAN, that sound is SO good !

I forgot what a nice cart that 8-T is.