Adding 1/4 track head to AG 440B

jimhumphries

New Member
I've read many fine accounts of refurbishment projects for Ampex AG 440s and I was lucky enough recently to purchase one. In addition to restoring it to working condition I wanted to add a quarter-track stereo head so that I could enjoy my commercial pre-recorded tapes. The attached PDF is an account of my project. I thought it might be of interest to other RTR DIYers.
 

Attachments

  • Ampex 440 Notes.pdf
    2.6 MB · Views: 23
Certainly a well executed effort and a great write-up of the significant amount of work involved in doing this!
 
Nice deck and write-up, and good execution as well.
Spent a lot of hours running these 'back in the day'. A couple tricks I recall:
1. Close head gate gently. Flipping it up will impact alignment over a short time.
2. Spin up the idler before you hit play, if you're spotting SFX, etc. Many films have the "warbling telephone bell" sound effect because folks didn't do it.
3. You can quickly get reverse play by wrapping the tape under the capstan, thru the gap (backwards) and back over the top of the pinch roller. Poof, instant reverse. Use expendable tape the first time you try this, as it will reveal transport inadequacies quickly (!).

If you're still having capstan tracking issues -- have you checked capstan shaft for uniform diameter, top to bottom? Any slight taper due to wear could show up as mistracking, if your new pinch roller doesn't fix things. (May have missed progress on this in the write-up...)

Nice job!

Chip
 
Nice deck and write-up, and good execution as well.
Spent a lot of hours running these 'back in the day'. A couple tricks I recall:
1. Close head gate gently. Flipping it up will impact alignment over a short time.
2. Spin up the idler before you hit play, if you're spotting SFX, etc. Many films have the "warbling telephone bell" sound effect because folks didn't do it.
3. You can quickly get reverse play by wrapping the tape under the capstan, thru the gap (backwards) and back over the top of the pinch roller. Poof, instant reverse. Use expendable tape the first time you try this, as it will reveal transport inadequacies quickly (!).

If you're still having capstan tracking issues -- have you checked capstan shaft for uniform diameter, top to bottom? Any slight taper due to wear could show up as mistracking, if your new pinch roller doesn't fix things. (May have missed progress on this in the write-up...)

Nice job!

Chip
Well, if we're going to do stupid analog tricks...
4. Masking tape around the capstan makes a good redneck pitch control. Record with masking tape on the capstan, then play back without and you can get monster voices!
5. Fun with tape loops. Get out that splicing block! Record some sound you want to loop. Cut it out of the reels and splice the ends together. Tape down the take up arm, thread the tape through the transport and loop the excess around a microphone stand to take up the slack.
 
Nice deck and write-up, and good execution as well.
Spent a lot of hours running these 'back in the day'. A couple tricks I recall:
1. Close head gate gently. Flipping it up will impact alignment over a short time.
2. Spin up the idler before you hit play, if you're spotting SFX, etc. Many films have the "warbling telephone bell" sound effect because folks didn't do it.
3. You can quickly get reverse play by wrapping the tape under the capstan, thru the gap (backwards) and back over the top of the pinch roller. Poof, instant reverse. Use expendable tape the first time you try this, as it will reveal transport inadequacies quickly (!).

If you're still having capstan tracking issues -- have you checked capstan shaft for uniform diameter, top to bottom? Any slight taper due to wear could show up as mistracking, if your new pinch roller doesn't fix things. (May have missed progress on this in the write-up...)

Nice job!

Chip
Thanks to all who have replied. It is a fun project and it was a pleasure to post it. I'm making good progress on equalization for the new quarter-track head and adjustment of the frequency response for the half-track heads. I'll write that up and post it for anyone interested. Chip: I haven't sent the pinch roller off to Terry yet but it's high up on the punch list. The tape drifting down the capstan is definitely related to the pinch roller. Regards, Jim
 
In the first part of the project notes (Ampex 440 Notes) a 440B was restored to operating condition, upgraded from full-track, single channel to half-track, two channel and a quarter-track playback head and a half-track/quarter track selector switch were added. In this second part the condition of the electronics are assessed (including the heads) and adjustments are made using inexpensive PC based software to achieve a desirable performance level (factory specification is the target). Experimenting is begun to equalize a quarter-track playback head using passive components so that readjustment of the EQ for half-track playback is avoided. Apologies in advance for the (too) many graphs.
 

Attachments

  • Ampex 440 Notes (part2).pdf
    889.5 KB · Views: 5
Factory spec very conservative and the bare minimum the machine is guaranteed capable of here. Not good enough for you or for Ampex, get it to what the machine is really capable of and not "Close Enough" as that is not Ampex's way of building a deck.
 
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