Mercury Magnetics JTM 45/100 PT clone - compromised or not?

[mxrshiver]

got hired to gut a high gain custom boutique amp to install an original circuit, using basically just the previous iron, chassy, and hardware. the power transformer is a Mercury Magnetics FARG-HENDRX-P, a clone of the JTM 45/100 PT with a 435-0-435 high voltage winding and two 6.3VCT 5A windings.

the previous amp was made using excess heat/dwell time everywhere, including right up against component bodies, ruining several small components. it really looks like a soldering gun was used everywhere. that's just the start of the very scary poor soldering on the former amp, but it's the most relevant detail and i'm not making this post to bad-mouth anyone.

anyway. testing the power transformer for intented load of around 150mA total with 2x KT88's at about 580V plate and 550V screen (and hefty 2.2K screen stoppers), and 7x 12A_7 at 480-360V with DC heaters, all voltages are right as expected, all windings are loaded to a comfy 70-80% or so of their max capacity, and the big beautiful dope barely gets warm. perfect.

the issue is that two of the %#&%^@% transformer terminals don't connect to anything anymore.

see the photo - 12 numbered winding terminals, each with a pair of duplicate tags wired in parallel, one on either side of the number, the inner ones pointing towards the camera and the outer ones pointing towards the sides. for both number 2 (the 120V hot connection) and number 11 (one side of one of the 6.3V windings), the outer facing terminals read infinite resistance to all other terminals, including the ones intended to be connected directly to them on the other side of their numbers. in addition, these terminals are able to wiggle back and forth a bit, whereas none of the others can budge a single bit. and in terms of the amp's original wiring, both of these outer terminals did have solder on them but no wires were attached, only the inner ones were wired... leading me to think the wires were originally attached there, until it was discovered that they didn't work.

reached out to Mercury, it's their opinion that this likely happened due to excess soldering heat and pressure, and that as long as there weren't other issues with performance (the amp was functioning before teardown, even with the bad soldering), it most likely only presents an inconvenience and does not indicate further issues with the main, inner terminals, as long as they present proper voltages, are steady when loaded etc. but they also cannot guarantee it without looking at the transformer, and they offered to test it at no cost, but just 2 way shipping for this thing is probably gonna be at least $60+ and several weeks added to this job. i tried to ask a bit more about the internal structure, but that's as much info as i was able to get.

i'm at an impasse. i really don't want to give up this power transformer, and i'm not certain how concerned i should be about this. in addition, i'm not certain how much i trust Mercury Magnetics on this issue. every time i've contacted them in the past, i've always gotten great customer service that really tries to go the extra mile, but somewhere along the line, they end up being inconsistent or incorrect about their own specs, and i've never been impressed with the inflated pricing, lack of published specs, and pseudo-scientific 'articles' on the website. also, even though it was likely excess heat and pressure that dislodged them, i'm not impressed with how easy these terminals were to dislodge in the first place!

idk. i don't know how much i should be worried about this, and i'd HATE to waste so much iron without good reason... and if we do have to consider new iron, i'm not sure if i should go with another one of these to suit the current design, even though the old one messed up... or look to Hammond, Heyboer or Classictone replacements that i'd have no concerns about, but would have to redesign the circuit and layout around. most everyone on here is more experienced than me... what would you do? which option(s) or perspective(s) do you think you'd choose at this point?

A) this is nothing more than an inconvenience, no reason to worry, continue as usual with this PT just using the inner terminals

B) send to MM to get tested, use it with the inner terminals if it tests good, and if it tests bad at all, get it repaired if possible, or get a new MM one of the same type if not

C) same as B, but if it tests bad, get a Hammond, Heyboer or Classictone instead

D) just get a Hammond, Heyboer or Classictone now to be safe and stop cryin about the redesign


 thanks in advance!!

[BrianS]

Since you are being paid for your work, A is not an ethical option.  I'd personally choose B.
Good luck.

[mxrshiver]

thanks Brian! i would agree, no reason to risk option A.

[tubeswell]

Tell the owner that the amp has been butchered including the PT and it will need a new PT. If he’s not happy, decline the job.

[mxrshiver]

thanks tubeswell, fortunately the customer is max understanding and is willing to pay what it takes for quality and reliability, so i will likely be going that route.

my purpose here is more i  trying to evaluate if folks think it's worth continuing with MM for testing, and/or a new transformer, or if you'd just opt for a new transformer from a different company at this point and re-design accordingly. your response seems to indicate you'd probably choose option D in my shoes - is that correct? would you even consider B or C? thanks again for your advice!