Sony BVH-2180-PS: Servo Error

Want to know how something works? Harness the power of the Brainiacs!
MartinKuhnert
Posts: 6
Joined: Mon Mar 20, 2017 9:16 pm

Re: Sony BVH-2180-PS: Servo Error

Post by MartinKuhnert » Fri Mar 31, 2017 9:28 am

Hallo,

I got both Manuals now and started a lot of measuring... On TP 15 there seems to be nothing... But one thing seems strange ( maybe ) I have an NTSC version of CF-17 an when I put this board in, I get the same error ( after 15 seconds switch of and system error... Is this ok or does it mean that maybe both CD 17 boards I have are defective ?
thanks, martin

User avatar
PID_Stop
Posts: 482
Joined: Thu Apr 01, 2010 11:58 am
Location: Syracuse, New York
Contact:

Re: Sony BVH-2180-PS: Servo Error

Post by PID_Stop » Fri Mar 31, 2017 10:13 am

MartinKuhnert wrote:
Fri Mar 31, 2017 9:28 am
Hallo,

I got both Manuals now and started a lot of measuring... On TP 15 there seems to be nothing... But one thing seems strange ( maybe ) I have an NTSC version of CF-17 an when I put this board in, I get the same error ( after 15 seconds switch of and system error... Is this ok or does it mean that maybe both CD 17 boards I have are defective ?
thanks, martin
Hi Martin,

The drum servo runs in several different modes depending on what the machine is doing at the moment: for instance, with the machine in PLAY mode, the servo will position the drum 120° differently, depending on whether you have the R/P head selected or the dynamic tracking PLAY head. TP15 is active during playback with the R/P head, and you set the drum PG phase adjustment to line up the leading edge of a pulse on TP15 with the nearest leading edge on TP13 (you need at least a dual-trace oscilloscope for this). In Volume 1 of the manual, take a look at section "10-7, PG PHASE ADJUSTMENT" for a description of this; figure 10-23 shows the relationship between TP15 and TP13.

Two important corrections for the manual:
1) In section "A, Playback with R/P Head", make sure the control panel is switched to internal servo reference.
2) In section A, step 5 and step 6, change the phrase "VIDEO OUT" to "DEMOD OUT". You must be comparing VIDEO IN against the output of the demod, not the output of the time base corrector.

Having said this, I don't think the drum PG phase is the problem here. You can affirm this by trying to play a tape with both the R/P head and with the PLAY head; if you get the same alarm and shutdown, phase control probably isn't what's going wrong.

My next step would be to read through the theory of how the drum servo works; it's section 5-7-5 of volume 1, starting with part 5, Drum Velocity Loop. That will show you several sample waveforms for different test points during different operating modes. You might be able to spot some thing that's obviously wrong, which could lead you to the fault.

After that, I would take a look at the servo system alignment procedure -- but before you go there, let me know: there are serious errors and omissions in the manual, so I will need to dig through the class training book to find the correct procedures.

Jeff

Post Reply