Maybe You Have A Juicy Question?

[Rex Everything]

2 hours ago, RealMarkDeneen said:

6H30 Upgrade

 

The Merlin, BBX, and Peach have individually unique changes for 6H30. Because one of the PSU resistors needs to be changed to reduce plate voltage. Although the upgrade only involves a few parts, it can get tricky due to the many versions of each PCB.

 

The plate & cathode resistors change on that tube socket, and at least one PS resistor. But, to be sure it is right, you have to be able to use a DVM to check voltages, and you may need to "adjust" the size of the plate resistor to match the board version you have. Also, yuo may have to VISUALLY trace the plate load resistor trace on the PCB back to the PS to see which LC is feeding it.

 

Before anyone jumps into that, I will need to do some digging regarding the right voltages. I DON'T have a 6H30 unit here. My Peach is 6DJ8.

 

Cheers!

Mark

 

 

I can tell you mine has REV J printed on the board. Not sure if that helps.

 

I'll be waiting for your info as I've been interested in this swap from my BBX since you released the 6H30 version.

[Marvel]

Mark, you sent me a refurbed Merlin in late 2005, when some forum members chipped in to get it for me and my late wife.

 

I imagine it's one of the early  versions. I can take pictures of it. I've got a DVM and can solder.

 

(Craig sent me a parts list... not sure how it would match up with yours. I can post it here or send you a PM)

 

Bruce

[capo72]

Here is the plate I made up to move RCA from circuit board. Mark suggested just drilling into the existing back panel. I didn't want to do that for a couple of reasons. This plate uses existing chassis holes so it is reversible, although I don't know why you would want to go back. I also didn't like the idea of drilling 18 holes in the BBX. 1 stray metal chip from drilling could cause some serious problems if they were not completely cleared away. I think I just purchased the RCA jacks from Parts Express or Amazon.

[Rex Everything]

Quick follow up: I replaced the nylon spacers with aluminum and upgraded and relocated the bridge rectifier per suggestion.

Ran it about 14 hours yeasterday and on a singing now. Thanks Mark!

[RealMarkDeneen]

On 3/4/2023 at 7:16 AM, Rex Everything said:

Quick follow up: I replaced the nylon spacers with aluminum and upgraded and relocated the bridge rectifier per suggestion.

Ran it about 14 hours yeasterday and on a singing now. Thanks Mark!

 

Bravo! Nice to hear of another "recovered" unit!

[BNR_1]

On 2/23/2023 at 8:31 AM, RealMarkDeneen said:

Hi--

Can you do a few voltage checks?

 

1. Check AC voltage across the two green wires. Should be around 20VAC or so. If not "bad transformer".

2. If that AC is ok, check the DC volts on top of the LM350. That is the large TO-3 device sitting in the middle of the 2" square heat sink on top of the PCB. That should be 6.3VDC +/- 1/2V. If NOT, you will need to replace the bridge rectifier which can be seen in the first photo. It is the 1" square black part near the long white resistor.

 

I will have to provide you the instructions and the part # you need to buy. It is the #1 most common failure in the BBX. Bad choice of parts on my part. However, once fixed it will last a long long time.

Email me with the results: aroadrunner@protonmail.com

Cheers

Mark

Hello Mark:

 

To verify the AC voltage for the two green wires do you connect each lead of the DMM to each of the green wires setting DMM to AC?

 

Can you explain how to test the voltage of the LM350?

 

Regards

[RealMarkDeneen]

Hi--

For the green winding you set the DVM to AC Volts. Put one lead on each wire. You should get about 18V or something like that - I can't quite recall but something like that.

Now then, if you do that by slipping the probes into the white molex connector, you might NOT get a valid read because on some units the spring terminal crimp goes bad and you won't get any volltage reading. If such happens, you have to unplug the green wires, "re-crimp" the spring lug, re-insert them and try again. It is VERY RARE for the green winding to be burnt out, but not too rare for the spring lug to go bad.

 

Now, to check the LM350, just set your DVM to DC Volts, and place the black lead on the ground terminal of the chassis and touch the red lead to the top side shell of the LM350 which sits inside the 2" square black heat sink. This reading MUST BE at least 6.1VDC and can be as high as 6.5. If you get a reading like 5V, or 4.5V, that means the mounting has loosened up. There are four bolts holding it down. You have to retighten the 4 bolts to a "firm setting" but don't go crazy and tighten so much that the PCB flexes!! Be careful. That should bring the voltage back up to the proper range.

 

If you need more email me directly at aroadrunner@protonmail.com. We'll get it figured out!

Cheers,

Mark

 

 

 

[BNR_1]

On 5/5/2023 at 6:46 PM, RealMarkDeneen said:

Hi--

For the green winding you set the DVM to AC Volts. Put one lead on each wire. You should get about 18V or something like that - I can't quite recall but something like that.

Now then, if you do that by slipping the probes into the white molex connector, you might NOT get a valid read because on some units the spring terminal crimp goes bad and you won't get any volltage reading. If such happens, you have to unplug the green wires, "re-crimp" the spring lug, re-insert them and try again. It is VERY RARE for the green winding to be burnt out, but not too rare for the spring lug to go bad.

 

Now, to check the LM350, just set your DVM to DC Volts, and place the black lead on the ground terminal of the chassis and touch the red lead to the top side shell of the LM350 which sits inside the 2" square black heat sink. This reading MUST BE at least 6.1VDC and can be as high as 6.5. If you get a reading like 5V, or 4.5V, that means the mounting has loosened up. There are four bolts holding it down. You have to retighten the 4 bolts to a "firm setting" but don't go crazy and tighten so much that the PCB flexes!! Be careful. That should bring the voltage back up to the proper range.

 

If you need more email me directly at aroadrunner@protonmail.com. We'll get it figured out!

Cheers,

Mark

 

 

 

Thank you Mark for the quick reply.  I will test my pre.

 

Regards

[BNR_1]

On 5/5/2023 at 6:46 PM, RealMarkDeneen said:

Hi--

For the green winding you set the DVM to AC Volts. Put one lead on each wire. You should get about 18V or something like that - I can't quite recall but something like that.

Now then, if you do that by slipping the probes into the white molex connector, you might NOT get a valid read because on some units the spring terminal crimp goes bad and you won't get any volltage reading. If such happens, you have to unplug the green wires, "re-crimp" the spring lug, re-insert them and try again. It is VERY RARE for the green winding to be burnt out, but not too rare for the spring lug to go bad.

 

Now, to check the LM350, just set your DVM to DC Volts, and place the black lead on the ground terminal of the chassis and touch the red lead to the top side shell of the LM350 which sits inside the 2" square black heat sink. This reading MUST BE at least 6.1VDC and can be as high as 6.5. If you get a reading like 5V, or 4.5V, that means the mounting has loosened up. There are four bolts holding it down. You have to retighten the 4 bolts to a "firm setting" but don't go crazy and tighten so much that the PCB flexes!! Be careful. That should bring the voltage back up to the proper range.

 

If you need more email me directly at aroadrunner@protonmail.com. We'll get it figured out!

Cheers,

Mark

 

 

 

Hi Mark:

 

Well I checked the voltage across the two green wires from the transformer and read 13.52V AC.  As you indicated it was not that easy to read due to the DMM probes into the Molex.  It is not 18V but is the 13.52V AC within the proper design range?

 

Due to an existing issue with one of the green wires (loose in the Molex connector), I could not get a read on the LM350.  The spring clip for the green wire is broken and loose so I don't get a good contact with the Molex connector inserted and gold pins on the PCB.  The tube filament does not light up.

 

My next task is to replace the clips and Molex for the red, and two green wires.  The green wires due to the filament do draw a lot of current.  The Molex connector (brownish & scorch) looks similar to the images posted by Rex Everything (02.22.2023).  John Warren posting (02.26.2023 northreadingeng.com) shows that his measurements for X7-X8 (Peach II schematic) was 2.9 to 3.2 A.  I assume the Blueberry Extreme is similar.

[RealMarkDeneen]

Hi--

Yes, I think your green winding voltage is fine. It's the pins. You can fix the pins, but it might make more sense (knowing what we know now about the pins/molex trouble), to remove the molex header from the PCB and just solder the transformer to the PCB. Yes, that makes it harder to replace, but I don't think I ever replaced a transformer, so low risk of that.

 

If you do replace the spring pins don't rely on the crimp. Solder the pins to the wire.

 

Maybe you can send me a pic of the area around the Molex. I'd like to make sure the blue caps and big cement resistor are ok. And (sorry if you told me already), but have you replaced the bridge rectifier yet? If not, read back through this thread and there is good documentation on what to buy and how to replace it. It is a major weak spot of the unit. They cook, burn and fail at about the 5 year mark. Bad choice of parts on my part. But, it's pretty easy to remedy.

 

The BBX has one more tube than the Peach. Four versus 3. Probably a little higher current in total, but I'm guessing because the rectifiers have failed much more often on BBX than Peach.

 

Keep me posted...

Mark

 

 

[Marvel]

Mark, is there still a chance for a Merlin schematic? The only one I've seen is a Merlin II with a 6H30 tube in it

[RealMarkDeneen]

On 5/15/2023 at 6:54 PM, Marvel said:

Mark, is there still a chance for a Merlin schematic? The only one I've seen is a Merlin II with a 6H30 tube in it

 

Hi Bruce--

 

Not finding it at all. HOWEVER -- there is another way to skin the cat. The first Merrlin units used the EXACT same line stage parts as the original BlueBerry with the 6922/6DJ8. So, that has an 18k plate resistor, a 470 cathode resistor and a 10k grid input resistor. The plate feeds a 2uF cap with a 10k load resistor. If you markup the Super Merlin schematic that way, you have the original Merlin. 

Mark

[Marvel]

Many thanks! A project I really want to finish...

[BNR_1]

On 5/13/2023 at 12:04 PM, RealMarkDeneen said:

Hi--

Yes, I think your green winding voltage is fine. It's the pins. You can fix the pins, but it might make more sense (knowing what we know now about the pins/molex trouble), to remove the molex header from the PCB and just solder the transformer to the PCB. Yes, that makes it harder to replace, but I don't think I ever replaced a transformer, so low risk of that.

 

If you do replace the spring pins don't rely on the crimp. Solder the pins to the wire.

 

Maybe you can send me a pic of the area around the Molex. I'd like to make sure the blue caps and big cement resistor are ok. And (sorry if you told me already), but have you replaced the bridge rectifier yet? If not, read back through this thread and there is good documentation on what to buy and how to replace it. It is a major weak spot of the unit. They cook, burn and fail at about the 5 year mark. Bad choice of parts on my part. But, it's pretty easy to remedy.

 

The BBX has one more tube than the Peach. Four versus 3. Probably a little higher current in total, but I'm guessing because the rectifiers have failed much more often on BBX than Peach.

 

Keep me posted...

Mark

 

 

Hi Mark:

 

Got some good news.  I replaced the Molex connector & pins.  My friend is into pinball machines and fortunately he has the tool to crimp the pins.  I purchased new pins and molex from Digikey.  As an added insurance, as Mark suggested, I also soldered the pin besides crimping.  It works wells.  All powered up.

 

I noticed that my unit does not have the LM350K, but LM338K.  With the new Molex & crimps, it reads 6.485V DC.  Spot on to the to 6.5V as by design.

 

I am at least the 3rd owner of this unit, and the seller I purchaed it from did not have much info on the work done by the prior owner(s).  But the tube recitifier was replaced with diodes and the bridge rectifier was removed from the PCB and mounted (bolted) to the chasis.  This was likely to improve heat transfer.  I was able to determine the type - GBPC2501.  There was another marking, but I could not make it out.  N1S0435 or N180435 or NJS0435.  Anyway, this series of codes did not matter on google.  The GBPC2501 popped up on a number of electronic stores.  Is this the stock unit or a replacement?  I looked it up on Digikey and it has a peak reverse voltage of 100V and an average rectified current of 25A.

 

I compared it to the unit you recommended from Digikey 641-1381-ND (GBPC5006-G).  This unit has a peak reverse voltage of 600V and an average rectified current of 50A.  I assume regardless if my bridge rectifier is original or replaced but it may not be adequate compared to your recommendation.  Any thoughts?

 

Regards

[BNR_1]

If anyone is curious or has a similar issue with the Molex connector or crimp this is what I ordered from Digikey and it worked perfect.  This is for the connector with the 3 wires - red, green & green.

 

Molex connector - Part #WM2103-ND; Molex product #0009503051, 5 pin rectangular connector

Molex pins - Part #WM2300-ND (18 to 24 AWG); Molex product #0008500106, KK2478 series

 

I ordered by check so I avoided shipping and handling fees.  It took about 1-1/2 weeks from the time I dropped off the check and order form into the mailbox.

 

Just remember the Molex KK pins require a certain tool to crimp.  Fortnuately for me, my friend had the tool.  I guess you could carefully use other wire crimpers and solder the wire to the KK pin for added isurance.  Or as Mark suggested, remove the header pin from the PCB and solder the wire directly from the transformer to the PCB.

 

Regards

[RealMarkDeneen]

17 hours ago, BNR_1 said:

I assume regardless if my bridge rectifier is original or replaced but it may not be adequate compared to your recommendation.  Any thoughts?

 

WOW - - what a great post!

You are good to go with the rectifier he put in. It is a replacement for the original and it is best when mounted to the metal chassis. AOK!

 

You actually got the pins and molex too! Very well done! That tool back when I bought it was about $75 -- I no longer have it.

 

Sounds like you are going to stay with the SS rectifiers in place of the 12X4?

 

And yes, the LMXXX at 6.4 is perfect - all good there.

So, are you back in business with a working unit now?

 

Cheers,

Mark

[BNR_1]

3 hours ago, RealMarkDeneen said:

 

WOW - - what a great post!

You are good to go with the rectifier he put in. It is a replacement for the original and it is best when mounted to the metal chassis. AOK!

 

You actually got the pins and molex too! Very well done! That tool back when I bought it was about $75 -- I no longer have it.

 

Sounds like you are going to stay with the SS rectifiers in place of the 12X4?

 

And yes, the LMXXX at 6.4 is perfect - all good there.

So, are you back in business with a working unit now?

 

Cheers,

Mark

Hi Mark:

 

I was fortunate that my friend has the tool for the KK pins.  If not, I would have probably done what you recommended and that is removing the header pin and solder the wires directly to the PCB.  But with the new Molex connector and pins it works perfect.  I am back in business listening to music.

 

Does the sonic quality improve with the 12X4 rectifier?  All I have as a point of reference is with the SS diodes in lieu of the 12X4 tube.  Is it difficult reversing it?  Also, I read others doing the SS diode mod.  Do you know why anyone would have performed such mod versus simply leaving it with a tube? 

 

BTW, thanks for confirming that my brige rectfier is sufficient.

 

Regards

[RealMarkDeneen]

I have two reasons to recommend the tube versus SS diodes. First, I like the sound of tube rectification, and I like keeping a certain "tube vibe" to the product. Second, the design of the circuit used the voltage as produced by the 12X4. Using SS diodes will raise all voltages in the plate circuits. Maybe it's audible, maybe not, but there's at least a theoretical reason to have the circuit "be as designed." When I twiddled each gain circuit, I optimized the loads and voltages by watching the meter on a precision distortion analyzer to achieve "minimal THD" for each tube stage. The BBX and Peach circuits do NOT USE feedback to lower THD as most other tube circuits do.BBX is a zero feedback design. Thus the "optimal voltages and loads" as designed would offer the lowest THD. Can we hear it? Well, I used to think I could - today probably not at 75 years old. In summary - a small difference is likely when changing to SS.

 

Cheers,

Mark

[the real Duke Spinner]

I prefer the ," softer" sound of a tube rec

 

[Rex Everything]

6DJ8/6922 vs 6H30

 

Any experience or thoughts on the 6DJ8/6922 tube vs the 6H30 Super Tube in the BBX?

 

I've got the info to convert mine from 6922 to 6H30 and have been considering it but wanted some opinions from members here who may have experience with both.

 

TIA!