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How I refurbished my first receiver (Marantz 2245)

CosmoK

CosmoK

Active Member
I recently refurbished a Marantz 2245 receiver with very little prior experience in electronics. I'm using this thread to collate my sources and comments, in hopes that they may help other beginners. The idea is to explain some of the basics and then reference the real sources of detailed information. I'd be grateful for comments on where I might have done something different or better. I'd also like to thank Audiokarma and all it's contributors, I have spent hours reading these forums and could not have done the restoration without them.

I'll put info on various aspects in separate posts for easy reference.
 
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Tools: Online, I bought a Hakko FX888D soldering iron, Kester 44 solder (63/37, 0.031"), a cheap solder sucker, solder wick, straight and curved anti-static electronics tweezers, a Fluke 116 digital multimeter (DMM, probably way overkill), cheap wire strippers. At Home Depot, I bought shrink tubing, zip ties, 600 grit sand paper, safety glasses, a single outlet GFCI adapter (not sure if this would actually save me), and a cheap part organizer tray. From Radio Shack, I bought Control/Contact Cleaner and Lubricant (most people prefer Deoxit), compressed air, and hook up wire. I already owned screw drivers, wrenches, scissors, pens/paper, electrical tape, 70% isopropyl alcohol (Walmart carries 90%, which is better), paper towels, a toothbrush, Q-tips, coffee filters (which I sometimes use in place of lint free Kimwipes), a flash light, and a fan.
 
Learning to Solder: I watched the youtube soldering tutorials on EEVblog, which explained the necessary gear and fundamentals of soldering. I then pulled apart an old alarm clock and practiced desoldering and re-soldering capacitors. I also practiced soldering hook up wire together.

 
Dim Bulb Tester: When you plug in an old receiver for the first time, or when you plug it in after working on it, you want to put it in series with lightbulb, so that if there is a short in the receiver (because of a solder bridge etc) the resistance in the lightbulb limits the current flowing through your receiver (i.e., prevents components in your receiver from melting, etc.). I built a dim-bulb tester from this Audiokarma thread http://www.audiokarma.org/forums/index.php?threads/compact-dim-bulb-tester-wiring.465423/ , although I wont go into detail about buying parts etc. I will note that: (1) building a device to run off wall power was a big confidence booster (and useful for general household repairs), (2) I got a dim glow from a 40 W bulb even when the receiver was fine, and a low watt bulb may prevent the relay from clicking in larger receivers, (3) leaving the receiver plugged into the dim bulb tester screwed up the power supply voltage adjustment (see below).
 
Cleaning: I begin by scrubbing the outside of the receiver with alcohol, removing the case and blowing out the dust with compressed air, and then removing the knobs and spraying contact cleaner into the potentiometers (pots) and switches behind the front panel. I literally, looked for all the small openings in the parts and gave them a quick shot of cleaner, then worked the knob/switch back and forth 100 times. I didn't worry about a little cleaner dripping on the circuit boards. I also sprayed cleaner in the speaker jacks and wiped out all the inputs/outputs with a Q-tip dipped in alcohol. I was surprised how much this cleaning improved signal strength to the speakers and removed scratchiness in the controls. After this, I could remove the input and turn the volume way up (slowly) and press switches and adjust knobs without hearing any static.
 
Marantz Documentation: The service manual (different from the owners manual) is available at HiFi Engine and contains the locations and layouts of the various circuit boards, which people often reference. The components have locations labeled with names like R802, which means the second resistor on the 800 (power supply) board. C is used for capacitor and H is used for solid-state/semiconductor components (i.e., transistors and diodes). The appendix of the service manual then lists the specs of each component (note: the left column of the component list for the P800 board is partially cutoff in the photocopy). However, the service manual may not always agree with what you actually find in your receiver (or the codes that are printed on the actually silkscreen printed on circuit boards).
 
Replacing Capacitors (re-capping): The key to restoring the receiver's sound is replacing the electrolytic capacitors. First a bit of background. Capacitors are defined by their capacitance (typically 0.1 to 10,000 micro farads), a voltage tolerance (typically 10 to 200 Volts), a temperature rating (typically 85 or 105 C), physical size and dimensions (larger capacitances and higher voltages typically mean larger components), ripple current (a performance measure), and construction material. The receiver has lots of ceramic capacitors (these are disks), lots of high-quality film capacitors in the audio path (these are (mostly) rectangular), a couple tantalum capacitors, and lots of electrolytic capacitors in both the power and audio paths (these are can shaped capacitors with both leads on the same end). Only the tantalum and electrolytic capacitors degrade significantly over time and need to be replaced.

Catrafter has lists of the capacitors that need to be replaced (see http://www.audiokarma.org/forums/index.php?threads/2245-cap-list.267889/). But, you can also try looking up the capacitors in the service manual, or better yet, open up your receiver and read the capacitance and voltage values off of the capacitors presently installed on each circuit board. When buying replacements, you should match the capacitance, but can always use higher voltages, provided the capacitor is still small enough to fit on the board. A 105 C temperature rating is best, but 85 C rating is fine. I bought all Elna Silmic II electrolytic capacitors through Digi-Key. Patfont has listened to many capacitors and recommends this line for Marantz receivers (http://www.audiokarma.org/forums/in...really-nice-rebuild-marantz-2245-2270.477423/), although catrafter's list gives the Digi-Key part numbers for panasonic capacitors, which many people also like.

I started by replacing the two main filter capacitors (the giant electrolytic capacitors that are not on a circuit board). I used Kemet ALC10 10,000uF/63V capacitors from Digi-Key, as shown at http://retrovoltage.com/2014/09/19/marantz-2245-stereophonic-receiver-rebuild/. They key here was to match the 40mm diameter of the original capacitor so that new capacitor fit in the existing clamps. When taking out the original capacitors, I cut as little wire as possible and then spent a long time sucking solder out of the original joints. I also drew a picture and marked the positive and negative terminals as well as the colors of the all the wires that were connected at each spot. When putting in the new capacitors I had to look up the locations of the positive and negative terminals on the new capacitors using the Kemet ALC10 data sheet. I then bent the grounding bar to touch the new capacitor posts and used a few wraps of very thin wire to hold the bar to the post while I soldered the whole thing together. I then checked the polarity of the capacitors two more times, if you put electrolytic capacitors in backward they explode. When I had the confidence to turn the receiver back on (first using the dim bulb tester), the receiver was notably fuller sounding. This was probably the single biggest improvement to the receiver.

Next, I replaced the capacitors on the power supply board (P800). When removing screws and other parts from the receiver, I placed the parts in an organizer tray with a paper note stating where it came from. I did not cut any wires. I then drew the board on a piece of paper and noted the values and polarity of each capacitor as I removed it (these may or may not match the service manual). I then dropped in the replacement and triple checked the polarity (the Elna Silmic II capacitors have a longer + lead and there is a band marking on the negative side). See http://www.audiokarma.org/forums/index.php?threads/one-idiots-guide-to-rebuilding-the-2245.462080/ for excellent notes on this board (and a cautionary tale about putting capacitors in backward). Upon turning the receiver on, this was the second biggest improvement in sound.

After that I recapped the tone (pre-amp) board (P400), phono board (P700), and left and right amp boards (P750). Testing the receiver after each board. Some of these boards are difficult to work on without cutting wires, but it is possible. I did not re-cap the AM/FM boards.

At this point, you could call it a day, but there is a lot of discussion about adding bypass capacitors and replacing good original film capacitors with fancy film capacitors (e.g., sonicaps, Jantzen, etc.). Note that film capacitors are not typically polarized, so you can put them in any direction, even if the circuit board indicates specific positions for the +/- leads. Bypasses and film replacements are are discussed at length by Patfont during his 2245 rebuild (http://www.audiokarma.org/forums/in...really-nice-rebuild-marantz-2245-2270.477423/), but he did not use bypass caps or replace films later when rebuilding a 2230 (http://www.audiokarma.org/forums/in...tz-2230-throw-down-whats-all-the-buzz.550670/). I didn't read the 2230 thread until I was finished and ended replacing a bunch of original films with Panasonic films, only to re install the originals later. Although, I ended up leaving in some sonic caps and some Jantzen Superior caps, since they were expensive and the receiver sounded great.
 
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Transistors: The receiver has many transistors, some are cheap-looking black bits of plastic with three legs mounted on a circuit board, others look like large silver buttons (note: the specific shape of the transistor is actually denoted by a code: TO-66, TO-92, etc.). The output transistors are the silver buttons mounted on the heat sinks (black grills). There is also a button transistor connected to the power supply board. These large transistors need to conduct heat, but not electricity, into the metal parts they are mounted on. Hence, they need to be periodically "greased" with thermal paste (that conducts heat but not electricity), which looks like diaper cream. To do this, you can simply unscrew the transistor, pull it off, put a bit of paste on the plastic insulator between the transistor and mount point and put the transistor back into place. No soldering required.

Some of the small black transistors on the circuit boards may also need to be replaced. After the recap, I was getting some noise on one channel of the phono. I tried re-soldering the wires from the RCA jack to the board. This was a pain the neck and did not fix the problem. Finally, I decided to follow Patfont's rebuild and replace two transistors (H705 and H706, with part KSC1845 from Mouser) and three diodes (little balls at H707, H708, H709, with part 1N4448 from Mouser (two in series are required at H709)) on the phono board. First time around I forgot to put two in diodes in series at H708 and got no sound, which was unnerving, but an easy fix. Transistors from the same batch can have slightly different DC gains (Hfe). So, I borrowed a cheap DMM from a friend, which had a Hfe tester (high-end DMMs don't typically measure Hfe), and matched two transistors for H705 and H706, which work on the left and right channels. The actual Hfe varies substantially with temperature and is not so important (I saw the same transistor read 395-430 Hfe in rooms of different temperature), but getting two transistors with matching Hfe is important. I found a match after about 4 transistors, but most people recommend ordering at least 30, since they are only a few pennies each, and finding a good match may take several tries. When actually installing the transistors it is important to match the emitter (e), collector (c), and base (b) pin-out leads. I determined the configuration on the new transistors while using the DMM to measure Hfe (the meter has labeled e, c, and b inputs), I then double checked the old transistor's pinout by checking their Hfe. The e, c, and b markings are on the circuit board. Replacing the transistors removed the noise in my phono section. In general, it is common for failed transistors to cause problems, replacements for many styles have been identified by AKers (http://www.audiokarma.org/forums/index.php?threads/marantz-transistor-cross-reference.542746/)
 
Lights: The 2245 takes 7 fuse lamps and several smaller indicator lights. You can order kits that just contain the fuse lamps, or kits that contain all the lights. I bought a full set of lights with blue LED fuse lamps. The fuse lamps can be installed without cutting any wires or soldering anything, although they are a pain in the neck because there isn't much room to work. I did not replace any indicator lights because the originals were still working. The blue LED lighting is relatively harsh, and I do not like it compared to the softer original fuse lighting in a 2285B that I have. I have since put warm white LEDs in the 2285B, and it looks just like the originals. I wish I would have gotten warm white LEDs for the 2245.
 
Audio Adjustment: The last step in my restoration (actually I did this several times along the way) is to set the voltage on the power supply board (P800) and adjust the DC offset and idle-line current on both amplifier boards (P750). This is described in the service manual. Before doing these procedures, make sure you have probes that are mostly covered and attach securely to the posts (I use ones with retractable hooks). If your probes are not isolated and they slip and hit a transistor, the resulting short may destroy that component. See this cautionary tale: http://www.audiokarma.org/forums/in...cant-adjust-j802-j803-to-35v-loud-hum.402612/.

During the first part of the procedure, I could not get a high enough voltage on the power supply board (32.5V instead of 35V), because I tried to do it with my receiver plugged into the dim bulb tester. Before figuring out I simply needed to plug my receiver into the wall to fix the problem, I replaced the relay (L801) and a transistor (H806), which may have had the nice effect of reducing noise in the receiver (but maybe that's just me). The DC offsets are easy to set to zero, and my understanding is that this helps protect the tweeters on your speakers. If you can't find the potentiometers, note that because one amp board is flipped, some pots are accessed through the bottom of the receiver. The idle-current adjustment is tricky because the service manual is wrong, you need to measure between J754 and J760 and adjust the AC voltage to 10mV (see http://www.audiokarma.org/forums/in...-2245-idle-current-this-cant-be-right.375509/).
 
Cost Analysis: The actual capacitors, lights, transistors, and diodes totaled about $150 (I think), you could easily add/subtract $50 by buying higher or lower quality capacitors or skipping a few parts of the restoration. The soldering iron, DMM, cleaning supplies, and other parts and tools probably added up to $400, but most of this went toward the quality soldering iron and my expensive DMM.
 
Sound Analysis: You don't need to be an audiophile to appreciate the sonic improvements obtained through this restoration, although I'm not certain I could hear major incremental improvements after re-capping every single board. But, I am not musically gifted, I don't have very fancy speakers, and my ears are not well trained. To me, the final sound is warm and generally awesome. Vinyl sources sound significantly better (fuller, more 3D) than ipod sources, this was obvious and confirmed/described by several people in blind listening tests.
 
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Wow, quite a write-up ! thank you for putting all this info down. I'm doing a 2245 myself at the moment, so your thread might come in handy...
How about some pictures :D ? sorry - couldn't resist...
Yes, about the warm-white leds, they look very close to original. I did all the rest with led as well, but this needs putting in place dropping resistors and small rectifier / cap assemblies for the dial needle and the function indicators. ("stereo" indicator is already fed DC)
Yesterday I was trying to adjust the idle, also with the DBT, no good, it needs to be plugged-in straight...
And yes from my experience as well recapping gives a good sonic improvement.
 
I spent about two months working on this restoration, and I wanted to wait until it was done (and successful) before putting all the info together. Hopefully there is a nugget or two of useful information in there.
Bert 1100 said:
How about some pictures :D ? sorry - couldn't resist...
Click to expand...
Unfortunately, the only pictures I produced are badly drawn diagrams of the capacitors extracted from each circuit board! Many thanks to those who do post pictures though, they're definitely useful.
 
one last aspect of the rebuild…

Power Button Failure: After a couple of weeks I suddenly turned the receiver on to find the dial lights flickering and a buzzing/crackling noise coming from behind the face plate. I diagnosed this as power-button failure due to arcing (maybe because I turned it on and off with the volume half-way up). Apparently, the switch can be completely replaced with Digi-Key part EG1018-ND. But, I followed this procedure to disassemble the switch and clean/sand the contacts: http://www.audiokarma.org/forums/in...ts-guide-to-rebuilding-the-2245.462080/page-3. It was a pain in the neck, but now the receiver works great again.
 
A lot of effort went into this write up and I commend your effort. I confess to not reading it totally but what I did read was correct. Glad you are enjoying the great new sound, I concur wholeheartedly that recapping is a must on this era of unit. I just found three bad caps in a 2225 yesterday with one lead completely pulled loose by the expanding innards.
 
Starquest said:
Agreed, excellent write-up. I've never recapped anything and it almost makes me want to try!
Click to expand...

I greatly enjoyed doing the restoration. Here are some amateur thoughts on another amateur doing a re-cap…

If you just want to re-cap a single beloved receiver, I suspect you will get better work for less money and risk by taking it to a good technician.

If you like the idea of learning some new skills and doing it yourself, and you have time and patience, I suggest you give it a shot. Although, you have to own the risks of (1) electrocution and (2) irreversibly damaging/destroying the receiver.

I follow some safety practices, but I'm not qualified to give advice on (1).

In terms of (2), I noticed these risks:
(i) Potential to break things due to mechanical stress while cleaning or trying to free up a circuit board, pull out a glued-down component, etc. There's a lot of brittle/fragile stuff in the receiver, and it's easy to get carried away. Sometimes a bump is all it takes to break an old solder joint or transistor. When a part wouldn't come loose, I kept reminding myself "a broken obsolete part is a much bigger problem than something being stuck."
(ii) Potential to overheat things with a 700+F soldering iron. I tried to take the time to get everything in the optimal position before soldering or desoldering. If I pressed the iron tip on a component for more than a few seconds and nothing happen, I backed off and re-assessed the situation before I thermally damaged the board or a component. If you're in a rush, it's also easy to unsolder the wrong lead, hit things with the soldering iron, accidentally melt wire insulation, etc.
(iii) Potential to frying components by turning on the receiver with an incorrect or backward part, or shorting them with a probe or solder bridge.
(iv) Potential to create new problems that can cause damage if they aren't fixed. Weird stuff happened during my rebuild: the phono board developed noise from failed transistors, the power switch started arcing (maybe it was my fault), and I initially adjusted the power board voltage wrong because of the dim bulb tester. A "simple" re-cap may require fixing other things in the receiver. Be okay with that.

Rereading (i)-(iv), I think you can mitigate most of these risks by being gentle, patient, and sober.

I'm sure some experts out there could identify other pit-falls. Come to think of it, I wouldn't mind reading a Marantz Audio "disaster story" thread if someone started one.
 
Look for the "I was adjusting the amp bias and the probes slipped and smoked arose from the board, now what do I do" threads! :oops::eek::yikes::(:dunno:

Another tip is if a solder joint won't flow when you're trying to desolder something, add a little fresh solder to get it going then desolder it with whatever method suits you.
 
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