An update to a discussion quite sometime ago in this thread about the location of the sonar on FLETCHER class destroyers based on what I have found out in my research at NARA. This isn't going to be exhaustive or answer questions for specific FLETCHERS, but shows in general and when specific sonar types were installed on FLETCHERS.
When FLETCHERS were designed and construction started they were intended to have THREE sound systems: a look down depth finding sonar (echo-sounding), and TWO search sonars operating in TWO different frequencies.
The basic installation for the search sonars were to be side by side at frame 25 on either side of the keel. The initial design had no domes, but then fixed domes were added over the projectors. This is what confused me from the BIW drawings, they only showed one side and said the other side was similar, but most records only mentioned one system. The depth-finding system was installed on the starboard side further aft at about frame 52-53.
Sonar projector sea chest.

Depth finding sea chest.

This overhead view shows where the three sound systems were located. The first few FLETCHER indeed had both search sonars installed. However, production of sonars couldn't keep up with demand with 100s of DEs being built besides all the other units designed to get sonar equipment, so it was decided to reduce the number of sonars to one on each new built fleet destroyers. One of the two sonars was ordered removed ... initially they said "pick one" ... either the starboard or port unit. However, it was eventually decided to "standardize" to installing the sonar on the portside since the "echo-sounding" (depth finder) was installed on the starboard side to reduce interference. It was hoped to at some point to go back to installing the second sonar, so installation of both sea chests continued on all construction.

In mid-1944 it was decided to install a new retractable sonar system, either QHB or QJB. Many FLETCHERS overhauled late in 1944 and into 1945 had this new sonar installed at about frame 25 ... the same location as before ... but on the centerline in a new sea chest built as part of the keel. This system was huge compared to the earlier sonar systems.


By the time FLETCHERS were recommissioned for the Korean War, the retractable sonar was considered obsolete and a new fixed sonar was installed ... eventually re-nomenclatured to SQS-10 ... in the same location at frame 25.

In the mid-1950s, about 1953-56, many FLETCHERS had the SQS-10 replaced with the newer SQS-4 sonar. This sonar was located at about frame 53. On some FLETCHERS the SQS-4 was installed in the forward location. Really confusing looking at Booklet of General Plans.
Docking plan for HAZELWOOD (DD-531) in 1953


PRESTON (DD-795)

Hopefully this helps to explain what really is a pretty confusing story. Sonars don't show up in photos often and as can be seen here, the systems did change over time.