This is our version for the ST-70 which uses ECF80 / 6BL8 / 6U8 / 6GH8 and ECF82 ...etc like tubes, instead of the lifeless 7199, and the main reason making ours.

Fully loaded of the new board are $299 cad including M-caps and metal film resistor. The board is drawn by ourselves at OEM par like how we drawn for our industry clients. Available extra for DC Balancer control for the EL34 output tubes to maximize durability and performance.

42 Watts output with even better distortion figures.

MORE: Convert to Super Dynaco is available.

For even better design, ask for our TDF ST-X version, which is available for $50- more, it uses 3 X 6922. It has nothing to do with the original ST-70, but It will more likely to give your Marantz 8B a go.  We like our ST-X more.

Diagnosis:  After our inspection, we have found quite more than usual parts need to go. Over 40 bits were needed to go. Here is what included on this usual up-to-spec service:

Solution: As always, we try to use all Japanese parts on these Japanese machine.The result is very nice now, perhaps many parts are being replaced, both side is making identical power at 39W at 1%, which is very good figure and is consider as good or better than NEW.

As there are quite a lot of these older Japanese receivers coming in recently for service. Here are the approximately costs to those who wanted to give their olde but good gears some refreshment. Clean up, Bench tested and Light bulbs all included:

Minimum: $20-90 (Average of $70) ; Medium (like this Pioneer): $140 - $220 (Average of $170-180)

*READ THIS* if you come across to these amps frequently.

Diagnosis:  Many of these amps are not protected by fuse, even it works, you are putting yourself in danger. Most parts and components on this type of amps are all dried up, you are risking yourself anytime if you are unsure if safety feature have been added to yours (Please bear in mind even all parts are updated, it doesn't help to increase safety).

Solution: As per customer request, we have added speaker binding posts, RCA inputs, On off switches, new power cord / IEC socket, volume control ... etc which are unusual modern features to be seen on this type of amps. Like this little Single Ended EL84 type tube amplifier here (Top / Bottom Photo), 95% of its parts are all defected, we did spent 6 fuse just to test all bugs to make sure it is in sound and safe condition. Even the last bit of resistor won't do if we don't swap it out for a new one.

This type of job will be north of $100 easily as there are too much work to do and like this amp, we just have to torn it all off to redo again. 90%+ parts have to be new too.

Photo on the left: 7189 Push Pull Amp, similar case with this EL84SE Amp, safety features are added, new modern type of speaker binding posts are added, as well a up to spec service job.

Diagnosis:  After our usual inspection, we found nothing wrong with the parts nor circuitry. The tubes are also good. With our experience, we immediately know its the tube sockets. Which is more a maintenance issue rather than a problem.

Solution: A new set of nice tube sockets + free inspection and benchtest.

Diagnosis:  After our inspection, we just have to turn our client down and tell him the truth that 99% of the parts are either at the end of its life or soon. There are also more than 2 switches and pots that are also damaged and there are no replacement. With half a dozen more old switches and pots in the path, the best thing to do is to convert it to a pure power amp, by passed all those front ends.

Solution: As 99% of the parts are bad (which is not as bad for us), all we have to do is strip it all off and rebuild it to the original - which is far quicker and easier. This is now virtually a new power amp with the original transformers, which is nicely designed and allow us to switch it to Autobias making it less headache with different tubes of 6L6GB&GC/5881. Making this a good example of 6L6 power amp.

Diagnosis:  The condition is not bad at all.

Solution: Brought it up to spec and exceeded original factory spec for just $130. Very charm amp we like. The MC225 is one of the best tube amp from MC, we like it and to some extend if power is not your first priority, It is better to its siblings from the design of the transformers, to the efficiency and linearity of the output tubes of 7591.I remember one of these driving the entire movie theatre solo!

Diagnosis: As always, we study the original design before we start out our own way of changes.

Solution: With our experience, we know the cause and effect of each changes thru out the circuitry as well the weakest link. Here, do not underestimate these little works we perform. The spec and S/N are greatly improved.

Diagnosis: Before we start, the customer or the previous tech has already changed many of its caps and resistors to new ones. Some configurations also looked to be altered. This is going to be a tough one as things are not in original state. And Yes. We spent over 3 days just to analysis the receiver, and another 3 days doing more than 6 different tests, swapping parts in and out to spot on all problems.  Doing one thing less just won't help.

Solution: At last, we can say out we almost had to redo the whole amp. But it should have years of maintenance free of ownership.

Diagnosis: First thing we do is to pin down the cause of humming, also putting things back in original design state. The preamp was looked by another tech, whom did some test/changes on the circuitry - but fail to put it back to the original way, even it didn't help fixed the problem.  This just doesn't help because it will stress out something else, soon or later. At last we were glad we found the problem.

Solution: For the upgrade. The owner love the original sound so much not allowing us to change any of its design. Its okay, all we do is spend more effort on the power supply, as well redesign the grounding routes to yield the best S/N spec. We also installed the best caps possible to the key spots. At last, we are happy to see another satisfying customer. 

Diagnosis: Some defect parts found, as well a failed bulb.

Solution: After bench test, this just perform and looks like new... we send our driver to meet the owner 300 km away from Toronto for meet up as we really do not want to risk the shipping part on such lovely condition Mc.

How soon they will fail? It all depends your luck. It could be day 1 or your third time switching the amp on, it often start with tizz and hum, or a fail tube. It could be lucky enough to serve you longer than a year. It all depends where the spikes explode while running in the amp, and if that part of the circuitry able to absorb the excitement. *** Remember many of these parts/components are no name brand / replicas which has no / poor quality and does not able to withstand the extra stress test - they probably won't withstand the rated limits. There is not a 100% cure for these amps, because some where else might burst the next day. These higher price tag import amps surely worth the name of garage queen - too much to fix, and too waste to dump off.

Another thing we want our audiophile friends to learn. DO NOT BUY 110V amp / equipments. It is just not running a bit hotter compare to real North American spec 115V-130V products! It does not work like how you might think. Its not just a few percentage of a difference. It is actually stressing the product a lot more. It approximately putting 15%-20% extra load to the design, which is far more than designed - no safe guard to be talking of and over the safety limits. Again *** Remember many of these parts/components are no name brand / replicas which has no / poor quality. It depends where it fails at different stages on the circuitry, it could causes safety hazard which we concern most, especially these large triode SE amps, we are talking about close to or over 1000V.

Diagnosis: No need further diagnosis. If you have similar amp and having problem. It is require another over rebuilt/redesign. Which you better off buying a new amp or buy our 845/211 copy - we can reuse some transformers and the tubes. Here, we actually fitted our own 845 design into the amp, with our professional skill on making PCBs, It fits perfectly with all mountings and tube sockets.

Those who really want one of these large DHT tube amp, good and affordable. Please contact us. Our version of either 845 or 211 will be one of the best out there world wide. We are expert of these triode tubes - we know where our design stands. With Hammond grades transformer, you are very high up enough. It all depends the quality of the transformers you want to spend at last.

Solution: We've seen design flaws on product from different countries around the world regardless big names or not (there are always some small but quality labels out there to be fair). Solution is to stay away from product like this without a distributor/dealer. The best thing to do is to consult with your dealer. If you cannot afford new, ask your dealer to seek for used/demo ones. Many times they can still give you warranty on them even it might not be fresh out of boxes.