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Analog cart recorder - Help needed

S

SFM-Ptgal

After a long absence here I am again ;D
Last week I've been testing a Criterion 90-2 R/PB Harris cart machine.
The main issue found was that If I leak the peak levels above zero the low freq. tend to distort, something like a rotten woofer. If I nicely keep the levels bellow zero... perfect! Can it be a caps issue?
The other issue is the noisy motor... But I can handle that, it's not affecting the overall performance.
 
SFM-Ptgal said:
After a long absence here I am again ;D
Last week I've been testing a Criterion 90-2 R/PB Harris cart machine.
The main issue found was that If I leak the peak levels above zero the low freq. tend to distort, something like a rotten woofer. If I nicely keep the levels bellow zero... perfect! Can it be a caps issue?
The other issue is the noisy motor... But I can handle that, it's not affecting the overall performance.
Click to expand...

For the motor - if you have a local bearing shop take them one of the old ones and they should be able to get you those. Its been several years but I believe that it has 2 in each motor - top and bottom - be sure to change both.

Caps were always the first attempt in those machines. Also if you are having problems with the tone detector cards re-cap them as well and you should be good to go.

Another trick - if you have problems withthe capstan being too slick get some crocus cloth but beware, you have to be VERY careful using it. If you do turn the motor by hand and use it VERY lightly.
 
Check to see if the record meter is properly calibrated. It may be set to read too low (that is, "O" on the meter represents too high a level for the carts you are using). Also run through the biasing procedure, and adjust the bias for the carts you are using.

Back when carts were still used there were various formulations of cart tape that allowed for much higher recording levels then "standard" tape. Thereby increasing the signal to noise ratio on playback. Your machine may have been set up for such tape, recording at the higher levels on normal tape may cause the tape to saturate (just like overdriving an AM carrier) producing the distortion you are hearing.
 
TomT said:
Check to see if the record meter is properly calibrated. It may be set to read too low (that is, "O" on the meter represents too high a level for the carts you are using). Also run through the biasing procedure, and adjust the bias for the carts you are using.

Back when carts were still used there were various formulations of cart tape that allowed for much higher recording levels then "standard" tape. Thereby increasing the signal to noise ratio on playback. Your machine may have been set up for such tape, recording at the higher levels on normal tape may cause the tape to saturate (just like overdriving an AM carrier) producing the distortion you are hearing.
Click to expand...

I'm back... I don't think it's a bias issue because I have a nice Sonifex cart recorder wich I messed with the bias and now it's a nice door stopper because I don't have means to correct the s*** I've done.
The distortion on the Harris recorder is just on the LF and I have to pull the levels quite a bit to have a wideband distortion like I have on the Sonifex recorder. According to this should I go on reccaping? Why caps should I replace? Just the elect. or all of them?

That cart recorder is a war tank ;D

Thanks!
 
There are usually only two types of caps that ever need replacing: electrolytic and tantalum.

For the electros, I usually only bother with low-value ones. It's really only worth replacing anything under 100uF unless it shows obvious signs of failure or measures low.

Tantalum caps need to be replaced regardless of condition or value. They have a nasty habit of going BANG for no apparent reason and their capacity seems to vary wildly from their stated value.
 
Just an update... I was told by someone from station that previously owned the equipement that I should decrease the input level out of the console and compensate with the front pannel att. It worked! This messed me because the ITC recorder that I have handles the standard levels (0 output-0 input) nicely.

About the noisy motors he suggested me to replace the bearings OR use graphite powder. I'm willing to try the 2nd. How should I perform the use of it? Just spread it freely like baby powder into the motor? ??? ;D
 
SFM-Ptgal said:
<snip> I have a nice Sonifex cart recorder wich I messed with the bias and now it's a nice door stopper because I don't have means to correct the s*** I've done.
</snip>
Click to expand...

Setting bias isn't too hard. It helps if you know the 'overbias' figure for your tape, but right off the top of my head I would say that running 1 dB overbias should work.

IIRC, what you do is record a 10 kHz tone and, while monitoring playback level, adjust the bias level until the recorded output peaks in level, then continue raising bias level until the output drops by one dB. Then you're set.

You may want to check/adjust your record EQ at that point.

An alternative method to set bias would be to adjust for minimum THD, but that's difficult in a cart environment where the S/N and wow/flutter can get in the way of meaningful measurements.

Good Luck!

David
 
Yes, bias is not difficult to set on that machine. On the caps--we used Criterion-90's for years. The big filter cap would last about 4 or 5 years. From memory, it is a Mallory CG series, maybe two of them. (I think I have one upstairs but am too lazy to go digging through all that junk). Memory hazy but might have been 1000 uf @ 50 volts, computer grade, that soldered into the main board.

Usually we could tell when the cap was going because it would start missing cue tones.

As a practical matter, any think like a cart machine that I got used I would automatically change the electrolytics. Usually safe to assume that the previous owner decided to retire rather than do any preventive maintenance.
 
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