Do all JVC VCRs have the same quality heads?
 

I mean just the head itself. I was thinking about it lately because i have an hr-s3500u and was wondering if other models had the same sVHS head but different software and filters added on along with physical differences like the dynamic drums on some JVC models. What makes a good VCR when you take out the internal TBCs and the different dials and switches for adjusting things?

Have not been able to locate the SM for the HR-S3500U or the 9500U but at least the HR-S4500U and HR-S7500U shares drum assembly part number. The 3500U doesn't have the dynamic drum system but though it may very well share the rest of the drum parts with those. The 9500U has a flying erase head I think so the part no for the upper drum will be different, no idea to what extent there are differences between the actual heads on different upper head assembly part nos from the same lineup and tv system, not much info on it.

JVC tended to share a fair bit between the models in one lineup on their later decks in general as seen in the attached video technical guide for the 1998/99 lineup.

Q: Do all JVC VCRs have the same quality heads?
A: No.

Varies, especially S-VHS with-TBC vs. S-VHS non-TBC models, or S-VHS vs. VHS.

Most S-VHS decks are quality, but exact quality varies.

In addition to TBCs, aspects such as heads and transport, and stability and tolerances, etc, are why you get those decks.

Some low end models do share same heads with high end models but that doesn't mean they have the same picture quality, It's what comes after the head in terms of signal processing is what's important, The head just picks up the high frequency RF signal, at that stage it hasn't been converted to a useful video signal yet.

FWIW the (NTSC) HR-S3500U FSM lists the part numbers
Upper Drum Assy - LP20030-007A.
Full Erase Head - NAH0001-001
AC Head - QAH0010-002

The (PAL) HR-S8600EU/S9600EU FSM lists
Upper Drum Assy as LP20030-017A
Full Erase Head - NAH0001-001
AC Head - QAH0010-004

The (NTSC) HR-S9600U FSM lists
Upper Drum Assy as LP20030-016A
Full Erase Head - NAH001-001
AC had - QAH0010-004

So while erase heads are the same part number the other heads have a slightly different number

Some drivers of differences in an upper drum would be whether or not the VCR has a flying erase head, separate EP and SP heads, and FM Audio (HiFi) heads.