Sunday, August 16, 2009

The Perils of Li'l Mar: Episodes 3 and 4

In our last episode it had become clear that Li'l Mar, the cute as a button, but sonically distressed Marantz 4220 quad receiver, was trouble. Evidently she is what might be described as high maintenance as we continue with the anthropomorphization of Li'l Mar. Episode 1 saw a routine re-capping of the phono and regulator boards, and Episode 2 involved a fairly challenging but successful recapping of the power amp. At this point the ugly reality was clear: something was seriously wrong with the front end of this receiver.

Receiver preamps are a physical challenge to work on. They are typically on boards that contain pots and switches, and are therefore attached directly to the back of the face plate. So first you have to pull the knobs, remove the control retaining screws and unscrew the face plate. But since the preamp controls the operation of the rest of the unit via a web of wires, lots of tugging (and sometimes snipping) is required to actually pull the board free and get sufficient room to maneuver with a soldering iron. And amidst the pots and wires lie a bevy of tiny caps inserted long ago by people with tiny, young fingers...

Marantz gear is generally well made. Some receivers, notably the 2275, are a joy to work on. However, many Marantz boards, especially the smallish and dense ones, are soldered in a manner that is very difficult to work on. The parts were mounted in the factory with the longish leads folded over, in many places leading to a bit of a tangle. Removing a single cap can disturb the leads of 4 or 5 other components. Often the lead you are trying to free lies at the bottom of a pile of leads, folded over every which way. And often these boards do not have the stoutest of traces. Hot pulls are out of the question, this work requires solder wick in vast quantities.

So, yes, Li'l Mar's preamp board was difficult to remove, and once removed, difficult to work on.

Episode 3 in this condensed tale of woe was the recapping of the preamp. It was tough going with several tiny traces vanishing despite careful wicking. A total of 19 caps were replaced on the board, seemingly for naught. The sound was cleaner, but still weird. Sigh. Balance sliders had little or no effect, one channel was weak, and the tone controls seemed to behave like balance pots.

Time passed, hope sprung anew. Episode 4 started with pulling the preamp board again in anticipation of a high gain, low noise transistor replacement orgy. But a bit of perusing revealed a lot of wires wandering through the quad board tacked upside down underneath the switching control rods running to the back of the unit. After a bit of agonizing I determined that recapping the quad board was the path of least resistance. Here's a close up, before the re-cap:

An hour, 2 snipped wires and 14 caps later the work was complete, for semi-naught. The weak channel seemed better, but nothing else improved. So it was time to replace 8 very tiny transistors in the preamp. Very slowly. Here's a closeup of the dangling, re-capped preamp:

Preamp caps are low value, tiny, two legged beasties that are fairly easy to locate on the solder side of the board. The three legged transistors are even smaller and not so easy to locate. And they are basically impossible to grab with a finger unless you are under the age of 12. After a very challenging effort, 8 transistors were replaced. Fingers were crossed and a listen taken with boards dangling and Mar on her side.

Hmm. The front channel seemed slightly better, but the rear channels were there. Significant improvement, but not a resolution. It seems there will be (at least) an Episode 5.

Tuesday, August 11, 2009

The Perils of Li'l Mar: Episode Two

When we last visited our intrepid hero trying to save Li'l Mar, little did we realize he was more at risk than the fair damsel! Li'l Mar is trouble, trouble! And our shouts of warning are not directed towards Li'l Mar in peril, but instead to warn our hero. Look out! Things are not what they seem!

Our first effort in restoring the Marantz 4220 replaced the caps on the regulator board and the phono board, pretty simple stuff. But the power amp board promised to be trickier to work with given the space limitations in the undersized chassis. Here's a gander from the left side of the chassis, heat sink backing the amp board. Buried down at the bottom is a metal sandwich around the 8 Toshiba 2SC790 output transistors.

The amp board put up a tussle but eventually was exposed enough to work on, although not easily. The still attached wires and the dangling outputs (don't break!) made for slow going. A total of 19 caps were replaced with Panasonic FCs:

The outputs had little black pads glued on them to seat them in the heat sink sandwich. Cute. And note the Toshiba TA7109P IC drivers, rare, but can be purchased from Acme if needed.

The driver board was re-sandwiched and replaced and we gave it a listen... and it was still weird. Weak in one channel, with odd behavior from the balance sliders. And the FM was barely there.

Ominous music swell from an unseen and properly functioning sound system (no, not Li' Mar) ... And here is nothin' but trouble:

Yes, time to mess with the preamp. Something is wrong with the tone control board. Lots of little caps in a very cramped space, with too many wires limiting your room to maneuver. Nothin' but trouble. But we will have to await the next episode of the Perils of Li'l Mar to see if our intrepid tech survives.

Saturday, August 8, 2009

Wallowing in the '70s: Graham Parker

Graham Parker is a seriously overlooked artist who got stuck in your humble author's brain pan back in the early '90s. For about 6 months he lived on my office cd player, from Howlin' Wind to Mona Lisa's Sister. His backing band, the Rumour, are actually the remnants of Brinsley Schwartz, who seemed to function as London's house band during my time living there in the latter half of 1972. I caught them as fill ins, featured performers and as a backing band for Frankie Miller. The Brinsleys are worthy of a post of their own some day. Nick Lowe of Rockpile and solo fame was a Brinsley and produced Parker's first album, Howlin' Wind in 1976.

First up from Graham, a bit of snarling pop from 1979's Squeezing Out Sparks:

Next up, this gem from the unfortunately obscure Real McCaw (1983) with Brinsley Schwartz (the person) backing on guitar: You Can't Take Love for Granted.

And this from Howlin' Wind: Don't Ask Me Questions. If you watch to the very end you will actually get to see Graham's eyes. Yep, he does like his shades.

And let's wrap it up with another off of Squeezing Out Sparks: Protection.