Workshop Investigation #01 Hammond 1590B vs 1550B

When I recently received news that a particular Australian electronics parts distributor was starting to bring in Hammond die cast aluminium enclosures I got really excited when I saw that the prices were going to be a kick in the pants yabbies to the usual overpriced suspects. It was only when I looked a little closer at the part numbers did I realise that this is not the Hammond 1590B beloved by manufacturers and DIY pedal nerds the world over. 
No, it's the Hammond 1550B that is on offer here.

OK I thought, let's get one in and see why there is a significant price difference here (significance subject to increase when purchasing commercial quantities).
There's surely got to be something wrong with it to be priced so differently from a 1590B right? 

So here is my little comparison of Hammond's new 1550B enclosure next to our old favourite the 1590B. 

Please note that the 1590B example I had was sitting around the workshop for a while so it is a little dull in comparison to its fresh out of the shrink wrap cousin. Don't let that colour your judgement. 

 1590B on left

1590B

The 1590B I examined is made in the EU. Which country exactly is 'EU'? This could have been made anywhere between Gibraltar and Finland. I'm tipping not in Germany though.

As I believe there may be concurrent production of this unit in Canada it would be interesting to run a comparison with a Canadian built unit. In the meantime we'll have to make do with the European version that Hammond are happy to put their name to. If anyone has any info on whether Canada still produces 1590B's or not feel free to comment. There seemed to be some internet based confusion on this issue when I searched for the topic on my google machine.

 1590B

Width at base     = 60.3mm

Width at top        = 59.3mm

Wall thickness     = 1.84 - 2.02mm

Length at base     = 111.8mm

Length at top      = 110.8mm

height with lid     = 31.3mm 

1550B

The 1550B is made in Taiwan. Nothing wrong there, Taiwan is a highly industrialised economy with a lot of clever people making some pretty high tech stuff, they can handle production of a small aluminium box just fine. 

1550B

Width at base     = 64.0mm

Width at top        = 63.3mm

Wall thickness     = 1.38 - 1.49mm

Length at base     = 114.6mm

Length at top      = 113.8mm

height with lid     = 30.3mm 

COMPARISON

The thinner side walls of the 1550B make it possible to flex the sides by pressing really hard on them but once the lid is on this is unlikely to be a problem. Unless you have a pretty strange pedal switching technique I can't see this as a huge disadvantage. Unless of course you need all of your music gear to be 'mil spec'.

  

1550B at left

The ejector pin marks on the 1550B are a lot more flush than the 1590B's which are actually substantially depressed. The ejector pin marks are in areas where there are unlikely to be pots or switches installed but with the stuff people are cramming into these boxes nowadays you never know. In my opinion the 1550B is the better finished interior in this regard. The only issue I can see with the 1550B is the recess where the model number is located may make it difficult to position pots, switches or stand offs if they overlap the edges. 

Much tighter radius on the 1590B at right. 

The 1550B doesn't have as tight a radius where the top meets the sides as the 1590B. This gives it a softer look that in my opinion is neither here nor there.

Softer looking 1550B at left

The finish at the mold separation on the 1590B in in my opinion pretty woeful. You can see the difference in some of these photos, on the 1550B the only mold separation finishing I could detect was well executed. The 1590B on the other hand is a mess with heavy ridging and distortion of the lines of the box occurring.

1590B lid at left. Note poor finish to edge.

6-32 screw at left.

Both units are supplied with reasonably good quality stainless steel screws. The screws for the 1550B I examined were maybe a little off spec at M3.28 as opposed to M3.5. With the lid sitting on each unit without the screws installed there is noticeably more sideways play in the 1550B lid caused by the placement of the lip. Obviously once the screws are installed all play disappears. If I were to use the 1550B for production I would probably think about supplying my own screws. 

1590B. Heavy handed finishing in evidence

1550B. Looks pretty clean

The difference in price would seem to indicate a corresponding reduction in quality but in my opinion I really think the cons of the 1590B that I examined are outweighed heavily by the pros of the 1550B. I'd be happy to use the 1550B in future projects and production.

Crucially though, will the 1550B fit a 9V battery in it? Of course it will.

Repair job #100

This gorgeous 1972 Fender Twin Reverb is in unbelievable original condition. Cosmetically it is stunning and electronically it is super clean with only minor maintenance issues taken care of over the years. It has that beautiful vintage Fender smell that all amp techs know and love.

That unmistakable smell of a vintage Fender

Who is Mr. Hand?

When it came in it was being readied for sale so a service was in order plus a few maintenance jobs. The badly mismatched quad of power valves was changed out for a matched quad of JJ's 6L6GC's.

The original valves on my valve matcher were giving me:

V1=68mA

V2=30mA

V3=43mA

V4=65mA

V5 vibrato valve was not functioning below '2' on the rate dial and was replaced. A dried out 20uF 500V filter cap needed replacing with a modern Sprague Atom equivalent.

I also replaced the 125V mains fuse with a 250V type. Its not the worst thing I've ever found in an amp's fuse holder but we might as well use the correct type of fuse for the country we are operating in.

Finally. the reverb really wasn't sounding that hot. After removing the tank it was discovered that one of the retaining springs holding the reverb spring mounting plate in a floating position had snapped. One of the reverb springs also had a broken mounting hook. With some parts taken off a donor tank and involving some very fine soldering I set about to repair the tank. After all was put back together it really had not changed dramatically, it being too 'pingy' and not very appealing when pushed up the dial. Just not very 'Fendery'.
After poking around with various tests on the reverb circuitry it was established by tank substitution that the tank itself was just not sounding right. A new Accutronics P-R4AB3C1B tank was ordered in and this tidied up the sound nicely.

A beautiful amp with fantastic originality value,

an absolute pleasure to work on

With thanks to Chris.

Car audio inspired FRANKENAMP

This is just crazy, an amp that has been heavily modified with a frightening level of DIY skill coupled with a generous scoop of ignorance, always a dangerous combination.It would seem that someone has taken all their knowledge of car audio principles (low voltage, high current) and tried to apply it to a garden variety Fender Blues Deville type valve combo (high voltage, low current).

Unless they were actually trying to install the whole thing into the dashboard of a car then I have no idea why anyone would butcher an amp in this fashion. Unfortunately the addition of an industrial type US mains plug indicates otherwise, unless they have a really weird car (or an RV). The 10G mains cable is just hilarious, "ya gotta keep that resistance down in order to get 'the tone'."

Now it's just a matter of getting the house rewired and having a word with the power utility company about restringing some nice 'gold flashed' cable between your house and the power station. Because we all know regular copper is next to useless for the efficient conduction of electrons. Oh, and make sure all your fancy new cabling is 'broken in' before installation.

It's a real pity we don't get to hear this little puppy in action but I don't blame Adam for not even bothering to turn it on. You'd want to be winding the variac up real slow if you did actually want to go that far with it.

But hey, I hope that in the course of performing these crazy mods the owner at least fixed up all the cold solder joints that are usually par for the course with this era of Fender combo ala the Hot Rod Devilles and Deluxes. These amps keep us techs in business big time, nice clean channel though...

I also hope they had a good time belting out the solo to November Rain while their house (or car) burned down around them.